1. Symantec/
  2. Security Response/
  3. W32.Yimfoca.B


Risk Level 1: Very Low

December 3, 2010
December 3, 2010 3:29:26 PM
Also Known As:
W32/Autorun-BQG [Sophos], CXmal/FkFldr-C [Sophos], Troj/Baal-C [Sophos], W32/PushBot-L [Sophos], Troj/Dloadr-DJG [Sophos]
Infection Length:
Systems Affected:
When the worm executes, it attempts to copy itself to the following location if the operating system is Windows Vista:

Otherwise, it copies itself to the following location:
C:\Documents and Settings\Administrator\Application Data\HEX-5823-6893-6818\jutched.exe

It then deletes the original copy of the worm.

The worm may also download and store a configuration file in the following location:

Next, the worm creates the following registry entry so that it executes whenever Windows starts:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run\"Java Update Manager" = "C:\Documents and Settings\Administrator\Application Data\HEX-5823-6893-6818\jutched.exe"

It also creates the following registry entries in order to add itself to the list of applications authorized by the Windows firewall:
  • HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List\"C:\Documents and Settings\Administrator\Application Data\HEX-5823-6893-6818\jutched.exe" = "C:\Documents and Settings\Administrator\Application Data\HEX-5823-6893-6818\jutched.exe:*:Enabled:Java Update Manager"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List\"C:\Documents and Settings\Administrator\Application Data\HEX-5823-6893-6818\jutched.exe" = "C:\Documents and Settings\Administrator\Application Data\HEX-5823-6893-6818\jutched.exe:*:Enabled:Java Update Manager"

Next, the worm may connect to the following location using TCP port 1866 where it receives commands and downloads configuration information:

The worm may download files specified in the configuration files to the %Temp% folder and execute them.

Next, the worm checks for any removable drives from C through Z. It then creates the following hidden folder on the removable drive:

The worm then searches for any folders on the removable drive. If a folder is found, the worm hides the folder and creates a .lnk file with the same name as the folder:
%DriveLetter%\[FOLDER NAME]s.lnk

The .lnk file is given a folder icon and points to a copy of the worm in the following location:
%DriveLetter%\8585485\[FOLDER NAME]s.exe

Next, the worm attempts to spread through the following instant messaging applications:
  • GTALK - Google Talk
  • ICQ
  • MSN

It sends the following messages to all contacts in the IM clients along with a link pointing to a copy of the worm:
  • mira esta fotografa :D [LINK TO A COPY OF THE WORM]
  • seen this?? :D [LINK TO A COPY OF THE WORM]
  • This is the funniest photo ever! [LINK TO A COPY OF THE WORM]
  • olhar para esta foto :D [LINK TO A COPY OF THE WORM]
  • Wie findest du das Foto? [LINK TO A COPY OF THE WORM]
  • se ps dette bildet :D [LINK TO A COPY OF THE WORM]
  • bekijk deze foto :D [LINK TO A COPY OF THE WORM]
  • poglej to fotografijo :D [LINK TO A COPY OF THE WORM]
  • pogledaj to slike :D [LINK TO A COPY OF THE WORM]
  • titta ps denna bild :D [LINK TO A COPY OF THE WORM]
  • pozrite sa na to fotografiu :D [LINK TO A COPY OF THE WORM]
  • uita-te la aceasta fotografie :D [LINK TO A COPY OF THE WORM]
  • katso tStS kuvaa :D [LINK TO A COPY OF THE WORM]
  • bu resmi bakmak :D [LINK TO A COPY OF THE WORM]
  • spojrzec na to zdjecie :D [LINK TO A COPY OF THE WORM]
  • nTzd meg a kTpet :D [LINK TO A COPY OF THE WORM]
  • ser ps dette billede :D [LINK TO A COPY OF THE WORM]
  • podfvejte se na mou fotku :D [LINK TO A COPY OF THE WORM]
  • guardare quest'immagine :D [LINK TO A COPY OF THE WORM]
  • regardez cette photo :D [LINK TO A COPY OF THE WORM]


Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.
Writeup By: Stephen Doherty
Summary| Technical Details| Removal

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