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http://www.melissavirus.com/ ----------------------------------------------------------------- Date: Mon, 5 Apr 1999 05:01:14 -0700 From: secedu@all.net Subject: Information Security Educators Mailing List 1999-03-30 --------------------------------------------- >From: "Rob Slade, doting grandpa of Ryan and Trevor" Date: Tue, 30 Mar 1999 16:51:23 -0800 The Melissa macro virus A report prepared by Robert M. Slade The following is an attempt to bring together the information about the Melissa virus. It is taken from the most reliable available sources. Additional sites have been listed at the end of the article. I have not added a copyright line to this message in order to allow it to be used as needed. I will be posting the latest updated version of this article at http://sun.soci.niu.edu/~rslade/melissa.txt and http://victoria.tc.ca/techrev/melissa.txt. The virus, generally referred to as W97M.Melissa.A (with some variations: Symantec, in a rather strained effort to be cute, seems to be calling it "Mailissa"), is a MS Word macro virus. This means that, if you don't use Word, you are safe. Completely safe. (Except for being dependent upon other people who might slow their/your mail server down. More on that later.) If you need to look at MS Word documents, there is a document viewer available (free, as it happens) >from Microsoft. This viewer will not execute macros, so it is safe >from infection. In the messages about Melissa, there have been many references to the mythical and non-existent "Good Times" virus. Note that simply reading the text of a message still cannot infect you. However, note also that many mailers, in the name of convenience, are becoming more and more automated, and much of this automation concerns running attached files for you. As Padgett Peterson, author of one of the best macro virus protection tools, has stated, "For years we have been saying you could not get a virus just by "opening E-Mail. That bug is being fixed." Melissa does not carry any specifically damaging payload. If the message is triggered there will be text added to the active document. The mailout function can cause a large number of messages to be generated very quickly, and this has caused the shutdown of a number of corporate mail servers. If you have Word set with macros disabled, then the virus will not active. However, relying on this protection is a very dangerous proposition. Previous macro viruses have also killed macro protection in Word, and this one does as well. The name "Melissa" comes from the class module that contains the virus. The name is also used in the registry flag set by the virus. The virus is spread, of course, by infected Word documents. What has made it the "bug du jour" is that it spreads *itself* via email. We have known about viruses being spread as attachments to email for a long time, and have been warning people not to execute attachments (or read Word documents sent as attachments) if you don't know where they came from. Happy99 is a good example: it has spread very widely in the past month by sending itself out as an email attachment whenever it infects a system. Melissa was originally posted to the alt.sex newsgroup. At that time it was LIST.DOC, and purported to be a list of passwords for sex sites. I have seen at least one message theorizing that Melissa is someone's ill-conceived punishment for viewers of pornography. This hypothesis is extremely unlikely. Sending a virus to a sex related newsgroup seems to be a reliable way to ensure that a number of stupid people will read and/or execute your program, and start your new virus off with a bang. (No pun intended.) If you get a message with a Melissa infected document, and do whatever you need to do to "invoke" the attachment, and have Word on your system as the default program for .doc files, Word starts up, reads in the document, and the macro is ready to start. If you have Word's "macro security" enabled (which is not the default) it will tell you that there is a macro in the document. Few people understand the import of the warning, and there is no distinction between legitimate macros and macro viruses. Because of a technical different between normal macros and "VBA objects," if you ask for a list of the macros in the document, Melissa will not show up. It will be visible if you use the Visual Basic Editor, but only after you have loaded the infected file. Assuming that the macro starts executing, several things happen. The virus first checks to see if Word 97 (Word 8) or Word 2000 (Word 9) is running. If so, it reduces the level of the security warnings on Word so that you will receive no future warnings. In Word97, the virus disables the Tools/Macro menu commands, the Confirm Conversions option, the MS Word macro virus protection, and the Save Normal Template prompt. It "upconverts" to Word 2000 quite nicely, and there disables the Tools/Macro/Security menu. Specifically, under Word 97 it blocks access to the Tools|Macro menu item, meaning you cannot check any macros. It also turns off the warnings for conversion, macro detection, and to save modifications to the NORMAL.DOT file. Under Word 2000 it blocks access to the menu item that allows you to raise your security level, and sets your macro virus detection to the lowest level, that is, none. (Since the access to the macro security menu item is blocked, I do not know how this feature can be reversed, other than programmatically or by reinstallation.) After this, the virus checks for the HKEY_CURRENT_USER\Software\Microsoft\Office\Melissa?\ registry key with a value of "... by Kwyjibo". (The "kwyjibo" entry seems to be a reference to the "Bart the Genius" episode of the "Simpsons" television program where this word was used to win a Scrabble match.) If this is the first time you have been infected (and this "first time" business is slightly complicated), then the macro starts up Outlook, in the background, and sends itself as an attachment to the "top" 50 names in *each* of your address lists. (Melissa will *not* use Outlook Express.) Most people have only one (the default is "Contacts"), but if you have more than one then Outlook will send more than 50 copies of the message. Outlook also sorts address lists such that mailing lists are at the top of the list, so this can get a much wider dispersal than just fifty copies of the message/virus. There was also a mention on one message about MAPI and Exchange servers, which may give access to a very large number of mailing lists. From other reports, though, people who use Exchange mail server are being particularly hard hit. Then again, people who use Exchange are probably also standardized on Word and Outlook. Some have suggested setting this registry key as a preventative measure, but note that it only prevents the mailout. It does not prevent infection. If you are infected, and the registry key is removed at a later date, then a mailout will be triggered the next time an infected document is read. Once the messages have been sent, the virus sets the Melissa flag in the registry, and looks for it to check whether or not to send itself out on subsequent infections. If the flag does not persist, then there will be subsequent mass mailings. Because the key is set in HKEY_CURRENT_USER, system administrators may have set permissions such that changes made are not saved, and thus the key will not persist. In addition, multiple users on the same machine will likely each trigger a separate mailout, and the probability of cross infection on a common machine is very high. Since it is a macro virus, it will infect your NORMAL.DOT, and will infect all documents thereafter. The macro within NORMAL.DOT is "Document_Close()" so that any document that is worked on will be infected when it is closed. When a document is infected the macro inserted is "Document_Open()" so that the macro runs when the document is opened. Note that *not* using Outlook does not protect you from the virus, it only means that the 50 copies will not be automatically sent out. If you use Word but not Outlook, you will still be infected, and may still send out infected documents on your own. The virus also will not invoke the mailout on Mac systems, but definitely can be stored and resent from Macs. At this time I do not have reliable information about whether it can reproduce on Macs (there is one report that it does), but the likelihood is that it can. Vesselin Bontchev has noted that the virus never explicitly terminates the Outlook program. It is possible that multiple copies may be invoked, and may create memory problems. However, this has not been confirmed, and is not probable given the "first time" flag that is set. The message appears to come from the person just infected, of course, since it really is sent from that machine. This means that when you get an "infected" message it will probably appear to come from someone you know and deal with. The subject line is "Important Message From: [name of sender]" with the name taken from the registration settings in Word. The test of the body states "Here is that document you asked for ... don't show anyone else ;-)". Thus, the message is easily identifiable: that subject line, the very brief message, and an attached Word document (file with a .doc extension to the filename). If you receive a message of this form *DO NOT OPEN THE DOCUMENT WITH WORD!* If you do not have alternate means or competent virus assistance, the best recourse is to delete the message, and attachment, and to send a message to the sender alerting them to the fact that they are, very likely, infected. Please note all the specifics in this paragraph, and do not start a panic by sending warnings to everyone who sends you any message with an attachment. However, please also note that, as with any Word macro virus, the source code travels with the infection, and it will be very easy to create modifications to Melissa. (The source code has already been posted to one Web site.) We will, no doubt very soon, start seeing many Melissa variants with different subjects and messages. There is already one similar Excel macro virus, called "Papa." The virus contains the text "Fred Cohen" and "all.net," leading one rather ignorant reporter to assume that Fred was the author. Dr. Cohen was the first person to do formal research into viral programs. There is a message that is displayed approximately one time in sixty. The exact trigger is if the current system time minute field matches the current system time day of the month field when the virus is run. In that case, you will "Twenty-two points, plus triple-word-score, plus fifty points for using all my letters. Game's over. I'm outta here." typed into your document. (This is another reference to the "Simpsons" episode referred to earlier.) One rather important point: the document passed is the active document, not necessarily the original posted on alt.sex. So, for example, if I am infected, and prepare some confidential information for you in Word, and send you an attachment with the Word document, containing sensitive information that neither you nor I want made public (say, the fact that Bill Gates is a jerk for having designed the technology this way), and you read it in Word, and you have Outlook on your machine, then that document will be mailed out to the top 50 people in your address book. Rather ironically, a clue to the identity of the perpetrator may have come from the identification number embedding scheme recently admitted by Microsoft as having been included with Office and Windows 98. A number of fixes for mail servers and mail filtering systems have been devised very quickly. However, note that not all of these have fully tested or debugged. One version that I saw would trap most of the warning messages about Melissa. Note that any Word document can be infected, and that an infected user may unintentionally send you an infected document. All Word documents, and indeed all Office files, should be checked for infection before you load them. Information and antiviral updates (some URLs are wrapped): http://www.cert.org/advisories/CA-99-04-Melissa-Macro-Virus.html http://www.ciac.org/ciac/bulletins/j-037.shtml ftp://ftp.complex.is/pub/macrdef2.zip http://www.complex.is/f-prot/f-prot.html http://chkpt.zdnet.com/chkpt/hud0007500a/www.zdnet.com/zdnn/stories/ news/0,4586,2233030,00.html http://www.zdnet.com/zdnn/special/melissavirus.html http://www.symantec.com/techsupp/mailissa.html http://www.antivirus.com/vinfo/security/sa032699.htm http://www.avp.com/melissa/melissa.html http://www.microsoft.com/security/bulletins/ms99-002.asp http://www.sendmail.com/blockmelissa.html ftp://ftp.rubyriver.com/pub/jhardin/antispam/procmail-security.html http://www.innosoft.com/iii/pmdf/virus-word-emergency.html http://www.sophos.com/downloads/ide/index.html#melissa http://www.avertlabs.com/public/datafiles/valerts/vinfo/melissa.asp http://www.pcworld.com/cgi-bin/pcwtoday?ID=10302 http://www.internetnews.com/bus-news/article/0,1087,3_89011,00.html http://cnn.com/TECH/computing/9903/29/melissa.copycat.idg/ http://www.pcworld.com/cgi-bin/pcwtoday?ID=10308 ====================== (quote inserted randomly by Pegasus Mailer) rslade@vcn.bc.ca rslade@sprint.ca robertslade@usa.net p1@canada.com AV tutorial : http://victoria.tc.ca/techrev/mnvrcv.htm http://victoria.tc.ca/techrev or http://sun.soci.niu.edu/~rslade ---------------------------------------------