Virus.Win32.Xpaj

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.

Description

The virus infects files stored in the folders:

• %system% (usually C:Windowssystem32)
• %ProgramFiles% (usually C:Program Files)
• Files in shared folders
• Files on removable media, remote (network) disks and virtual disks (RAM), files prepared for the copying of CDs
• The following files that certain registry keys contain links to:

  SoftwareMicrosoftWindowsCurrentVersionExplorerBrowser Helper SoftwareMicrosoftInternet ExplorerExtensions SoftwareMicrosoftInternet ExplorerUrlSearchHooks SoftwareMicrosoftWindowsCurrentVersionShell ExtensionsApprov SoftwareClassesDirectoryShellExContextMenuHandlers
  
  
  
  SoftwareClassesFolderShellExContextMenuHandlers
  
  
  
  SOFTWAREClassesProtocolFilter
  
  
  
  SOFTWAREMicrosoftWindowsCurrentVersionRun
  
  
  
  SOFTWAREClassesApplications
  
  
  
  SOFTWAREClientsStartMenuInternet
  
  
  
  SOFTWAREMicrosoftMultimedia
  
  
  
  SOFTWAREMicrosoftWindowsCurrentVersionApp Paths SOFTWAREMicrosoftWindowsCurrentVersionUninstall

If the file does not satisfy certain conditions, e.g. it is protected with SFC, is will not be infected.

It attempts to connect to remote control servers indicated in the virus body. If server connections cannot be established, it attempts to connect to servers whose domain names are generated by the virus following a certain algorithm. The virus can download additional encrypted modules from the control server, which are then executed in the infected system.

Please note

Several variants of this virus are known to exist. This description was written for a version current in August 2011.

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