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 spreading under Win32 systems. The virus infects Win32 executable files, attempts to send e-mail messages with infected attached files, as well as installs a backdoor component to download and spawn "plugins" on an affected system. The worm caused a global epidemic from September--October 2000.

The virus has an unusual structure. It consists of three different components that are run as stand-alone programs (Virus, e-mail Worm and Backdoor). The virus is the main component, and it keeps the worm and backdoor programs in its code in compressed form. While infecting the system, the virus extracts and spawns them:

Virus structure

 � The virus     � --> installs Worm and Backdoor to the system,
 � installation  �     then finds and infects Win32 executable files
 � and infection �
 � routines      �
 � Worm code     � --> is extracted to file and run as stand-alone program
 � (compressed)  �
 � Backdoor code � --> is extracted to file and run as stand-alone program
 � (compresses)  �

Infected EXE file

 � File code     �
 � and data      �
 �               �
 � Virus code:   �
 �� Installation��
 ��and infection��
 �� Worm        ��
 �� Backdoor    ��

The worm code does not contain all the necessary routines to infect the system, being sent as attach in an infected e-mail message (see below). The worm needs"help" from the virus component, and is sent as being infected by the virus (the worm file is infected by the virus as an ordinary file and then sent). The reason for such a method is unclear, but probably the components were written by different people.

The Virus component contains the text strings:

Software provide by [MATRiX] VX TeAm: Ultras, Mort, Nbk, LOrd DArk, Del_Armg0, Anaktos
Greetz: All VX guy in #virus and Vecna for help us
Visit us at:

The worm component contains the text strings:

Software provide by [MATRiX] VX team:
Ultras, Mort, Nbk, LOrd DArk, Del_Armg0, Anaktos
All VX guy on #virus channel and Vecna
Visit us:

The Backdoor contains the text:

Software provide by [MATRiX] team:
Ultras, Mort, Nbk, LOrd DArk, Del_Armg0, Anaktos
Vecna 4 source codes and ideas

The Virus Component

The virus uses "Entry Point Obscuring" technology while infecting a file. That means the virus does not affect the file at its entry code, but places a "Jump Virus" instruction somewhere in the middle of the file code section to make detection and disinfection procedures more complex. As a result, the virus is activated only in case a corresponding affected program's branch receives control.

The virus is also encrypted, so first of all, it decrypts itself when its code gains control. The virus then looks for the necessary Win32 API functions by scanning the Win32 kernel. To do this, the virus tries the Win9x, WinNT and Win2000 addresses.

The virus then looks for anti-virus programs active in the system and exits in case any of them are detected. The list of anti-virus programs the virus pays attention to appears as follows:

AntiViral Toolkit Pro
AVP Monitor
McAfee VirusScan
Central do McAfee VirusScan

Next, the virus installs its components to the system. They are decompressed installed to the Windows directory and then spawned. There are three files created, and they have a hidden attribute set and the following names:

IE_PACK.EXE - pure Worm code
WIN32.DLL - Worm code infected by the virus (as "Infected File" above)
MTX_.EXE - Backdoor code

The virus then infects Win32 executable PE EXE files in current, temporary, and Windows directories, and then exits.


To send infected messages, the worm uses technology that for the first time was found in the "Happy" Internet worm (a.k.a. Happy99, a.k.a. SKA).

The worm affects the WSOCK32.DLL file in the Windows system directory by appending a component of its code to the end of the file and hooking the "send" WSOCK32.DLL routine. As a result, the worm then monitors all data that are sent from an affected computer to the Internet.

Usually the WSOCK32.DLL file is in use at the moment the worm starts, and it is locked for writing. To avoid this, the worm uses a standard method: it creates a copy of the original WSOCK32.DLL with a WSOCK32.MTX name, affects that copy and then writes "replace original file with infected" to the WININIT.INI file:


where "C:WINDOWSSYSTEM" is the name of the Windows system directory and may differ depending on the name of the Windows directory installed.

Upon the next reboot, the infected WSOCK32 replaces the original one, and the worm gains access to data that are sent from the infected machine. The worm pays attention to Internet sites (Web, ftp) that are visited as well as to e-mail messages that are sent from a computer.

The very visible behavior of the virus is due to the fact that it prevents the ability of visiting several Internet sites, as well as disables sending messages to the same domains (they are anti-virus domain names). The virus detects them by four-letter combinations that appear as follows:


The worm also does not allow sending e-mail messages to these domains:

meditrade.* **

The worm also intercepts e-mail messages that are sent and attempts to send a duplicate message with an infected attachment to the same address (the same as "Happy" worm does). As a result, a victim address should receive two messages: first, is the original message, written by a sender; second, comes a message with an empty subject and text and an attached file that has one of the names that are selected by the worm depending on the current date:


As an attached file, the worm uses the WIN32.DLL file that has been dropped by the virus component.

Note: the worm does not drop the WIN32.DLL file, but uses that file to attach it to messages that are sent. So the "pure worm" is not able to spread more than once: being run on a victim machine, the worm will infect WSOCK32.DLL, but will not be able to send its copies further. To "fix this problem," the worm sends its infected copy (WIN32.DLL is a worm component infected by a virus component, see above).

The known worm modification has a bug in its spreading routine and email server in many cases fails to receive affected messages from infected machine. Despite on that if the system has Dial-up connection, or mail server is fast enough, the worm sends its copies with no problems.


Being run, a Backdoor component creates a new key in the system registry that indicates the machine is already infected:


In case this key exists, the Backdoor skips the installation procedure. Otherwise, it registers itself in the auto-run section:


where %WinDir% is Windows directory.

The Backdoor then stays active in Windows as a hidden application (service) and runs a routine that connects to some Internet server, obtains files from there and spawns them in the system. So, the Backdoor can infect the system with other viruses or install Trojan programs or more functional backdoors.

This component in the known virus version also has a bug that causes standard a Windows message about an error in application when a backdoor tries to access an Internet site.

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