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: Virus

Viruses replicate on the resources of the local machine. Unlike worms, viruses do not use network services to propagate or penetrate other computers. A copy of a virus will reach remote computers only if the infected object is, for some reason unrelated to the virus function, activated on another computer. For example: when infecting accessible disks, a virus penetrates a file located on a network resource a virus copies itself to a removable storage device or infects a file on a removable device a user sends an email with an infected attachment.

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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 per-process memory resident parasitic high-polymorphic Win32 virus. The virus infects PE EXE files that have .EXE, .SCR, and .CPL filename extensions. When run, the virus infects these files in current Windows and Windows system directories.

The virus also stays in the system memory as a component of the infected host program, gains access to KERNEL functions and intercepts 15 of them: file searching, opening, copying, moving functions, etc. When a PE EXE file is accessed by these functions, the virus infects it. As a result, the virus will infect all PE EXE programs that are accessed by the infected host program, and the virus will be active until the moment the host program exits.

While infecting a file, the virus encrypts its 8K code and is stored at the end of the file. Then the virus reads 8K of the victim file code, encrypts it and is also saved at the end of the file. That "cave" then is filled with virus polymorphic code that decrypts the main virus code and passes control there:

File infection

 �=============�        �==============�
 �Header       �        �Header        �
 �-------------�        �--------------� <---- Program entry address
 �Code section � ---�   �Polymorphic   �
 �             �    �   �virus routine � ----� Jump to main virus code
 �             �    �   �--------------�     �
 �             �    �   �              �     �
 �-------------�    �   �--------------�     �
 �Data section �    �   �Data section  �     �
 �             �    �   �              �     �
 �-------------�    �   �--------------�     �
 �etc.         �    �   �etc.          �     �
 L=============-    �   L==============-     �
                    �   �Encrypted     � <----
                    �   �virus code    �
                    �   �--------------� 
                    L-> �Encrypted     � 
                        �hist file code� 

The virus' polymorphic engine contains bugs and in some cases, the virus cannot decrypt its code, causing a standard Windows message about an error in the application.

On Fridays, and depending on the system date, the virus replaces StartPage for MS Internet Explorer and Netscape Navigator with a reference to the Web site:

The virus contains the "copyright" text:

[Virus TUAREG by The Mental Driller|29A]
- This virus has been designed for carrying the TUAREG engine -

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