Win32/Yimfoca [Threat Name] go to Threat

Win32/Yimfoca.AA [Threat Variant Name]

Category worm
Aliases (Kaspersky)
  W32.Yimfoca!gen2 (Symantec)
  Worm:Win32/Pushbot.gen!C (Microsoft)
Short description

Win32/Yimfoca.AA is a worm that spreads via IM and social networks. The worm serves as a backdoor. It can be controlled remotely.


When executed, the worm copies itself into the following location:

  • %windir%\­%variable1%.exe

The worm may create the following files:

  • %windir%\­%variable2%.dl
  • %windir%\­%variable3%.dl
  • %windir%\­%variable4%.png
  • %windir%\­%variable5%.jpg

In order to be executed on every system start, the worm sets the following Registry entries:

  • [HKEY_CURRENT_USER\­SOFTWARE\­Microsoft\­Windows\­CurrentVersion\­Run]
    • "%variable6%" = "%windir%\­%variable1%.exe"
  • [HKEY_LOCAL_MACHINE\­SOFTWARE\­Microsoft\­Windows\­CurrentVersion\­Run]
    • "%variable6%" = "%windir%\­%variable1%.exe"
  • [HKEY_LOCAL_MACHINE\­SOFTWARE\­Microsoft\­Windows NT\­CurrentVersion\­Terminal Server\­Install\­Software\­Microsoft\­Windows\­CurrentVersion\­Run]
    • "%variable6%" = "%windir%\­%variable1%.exe"

The following Registry entries are created:

  • [HKEY_LOCAL_MACHINE\­SYSTEM\­CurrentControlSet\­Services\­SharedAccess\­Parameters\­FirewallPolicy\­StandardProfile\­AuthorizedApplications\­List]
    • "%windir%\­%variable1%.exe" = "%variable6%:*:Enabled:%windir%\­%variable1%.exe"

The performed data entry creates an exception in the Windows Firewall program.

A string with variable content is used instead of %variable1-6% .


Win32/Yimfoca.AA is a worm that spreads via IM and social networks.

The programs affected include the following:

  • AIM
  • Yahoo Messenger
  • MSN Messenger
  • Skype

The following social networking sites are affected:

  • Facebook

The worm spreads through links which point to websites containing malware.

Information stealing

The worm collects the following information:

  • computer name
  • operating system version

The worm can send the information to a remote machine.

Other information

The worm acquires data and commands from a remote computer or the Internet.

The worm contains a list of (4) addresses.

The IRC protocol is used.

It can execute the following operations:

  • download files from a remote computer and/or the Internet
  • run executable files

The worm changes the home page of the following web browsers:

  • Internet Explorer

The worm may execute the following commands:

  • net stop wuauserv
  • sc config wuauserv start= disabled
  • netsh firewall add allowedprogram 1.exe 1 ENABLE
  • explorer.exe

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