Parent class: VirWare

Viruses and worms are malicious programs that self-replicate on computers or via computer networks without the user being aware; each subsequent copy of such malicious programs is also able to self-replicate. Malicious programs which spread via networks or infect remote machines when commanded to do so by the “owner” (e.g. Backdoors) or programs that create multiple copies that are unable to self-replicate are not part of the Viruses and Worms subclass. The main characteristic used to determine whether or not a program is classified as a separate behaviour within the Viruses and Worms subclass is how the program propagates (i.e. how the malicious program spreads copies of itself via local or network resources.) Most known worms are spread as files sent as email attachments, via a link to a web or FTP resource, via a link sent in an ICQ or IRC message, via P2P file sharing networks etc. Some worms spread as network packets; these directly penetrate the computer memory, and the worm code is then activated. Worms use the following techniques to penetrate remote computers and launch copies of themselves: social engineering (for example, an email message suggesting the user opens an attached file), exploiting network configuration errors (such as copying to a fully accessible disk), and exploiting loopholes in operating system and application security. Viruses can be divided in accordance with the method used to infect a computer:
  • file viruses
  • boot sector viruses
  • macro viruses
  • script viruses
Any program within this subclass can have additional Trojan functions. It should also be noted that many worms use more than one method in order to spread copies via networks.

Class: Email-Worm

Email-Worms spread via email. The worm sends a copy of itself as an attachment to an email message or a link to its file on a network resource (e.g. a URL to an infected file on a compromised website or a hacker-owned website). In the first case, the worm code activates when the infected attachment is opened (launched). In the second case, the code is activated when the link to the infected file is opened. In both case, the result is the same: the worm code is activated. Email-Worms use a range of methods to send infected emails. The most common are: using a direct connection to a SMTP server using the email directory built into the worm’s code using MS Outlook services using Windows MAPI functions. Email-Worms use a number of different sources to find email addresses to which infected emails will be sent: the address book in MS Outlook a WAB address database .txt files stored on the hard drive: the worm can identify which strings in text files are email addresses emails in the inbox (some Email-Worms even “reply” to emails found in the inbox) Many Email-Worms use more than one of the sources listed above. There are also other sources of email addresses, such as address books associated with web-based email services.

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Platform: Win32

Win32 is an API on Windows NT-based operating systems (Windows XP, Windows 7, etc.) that supports execution of 32-bit applications. One of the most widespread programming platforms in the world.


Technical Details

This is a virus-worm that spreads via Internet channels attached to e-mail messages as the SUPPL.DOC MS Word97 document. It was posted to several newsgroups in September 1999. This document was created by using the Russian MS Word97 edition, which means that the worm has Russian or xUSSR origin.

To install itself to the system, the worm uses a method that does not work under WinNT, and as a result, the worm is able to infect and spread itself from Win9x systems only.

The worm has a very dangerous payload: in one week after infecting a computer, the worm erases, on local and remote drives, the files with the following extensions:


The method of erasing is the same that was used by "ZippedFiles" worm, and damaged files are not recoverable.


The infected document has just one macro Document_Open that is automatically executed when MS Word opens the document. This macro copies its document to the Windows system directory with the ANTHRAX.INI name, then drops its DLL component (that is stored in the infected document) to the same directory with the DLL.TMP name. This DLL component is dropped via a compressed temporary DLL.LZH file.

The worm then adds renaming instructions to the WININIT.INI file. These instructions rename the WSOCK32.DLL with WSOCK33.DLL name and replace the WSOCK32.DLL with worm's DLL.TMP library. This trick causes Windows to replace its WSOCK32.DLL with a worm copy upon the next Windows restart.

On initializing its DLLs Windows loads infected (worm's) DLL instead of original ones, and as a result, the worm gets access to network functions.


On next Windows restart, the infected WSOCK32.DLL is loaded into the system memory and gets control. The worm at this moment gets access and intercepts all necessary library functions that the original WSOCK32 library does. For all of them except two, the worm just forwards requests to original functions, and for this purpose, the worm also loads the WSOCK33.DLL (original library) into the Windows memory.

The two functions are processed by the virus: their names are "send" and "connect". By using these functions, the worm intercepts sent emails from the infected computer, and attaches its copy to these e-mails as the SUPPL.DOC file.

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