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Net-Worm:W32/Koobface.CZ

First posted on 10 December 2008.
Source: SecurityHome

Aliases :

There are no other names known for Net-Worm:W32/Koobface.CZ.

Explanation :

A type of worm that replicates by sending complete, independent copies of itself over a network.

right]This worm attempts to spread via messages or comments containing malicious links, which are posted on social interaction websites. It is primarily associated with Facebook, but the worm's comments can also be found on other popular websites.

Infection

The worm spreads by posting a message containing a link to a malicious website on all of an infected user's site contacts. Social interaction websites that the worm targets are:

• bebo.com
• blackplanet.com
• facebook.com
• friendster.com
• myspace.com
• myyearbook.com

The routines in this malware directly target Bebo.com and do not use the other sites listed.

The messages or comments posted may vary and may appear as:

• There is always someone watching your ass!
  
• Are you sure this is your first acting experience?
• is it u there?

The malicious links accompanying the message may also vary and may appear as:

• http://findamything.com/go/be.php?4chd849=[...]e
• http://finditand.com/go/be.php?0e9c60ch=[...]e
• http://findit12.com/go/be.php?e7883ch7=[...]e

If a message recipient clicks on the link, they are redirected to:

• http://www.aibcvienna.org/[...]tube/be.07.exe

This malicious website masquerades as a YouTube webpage. The user is then informed that their "Flash Player is outdated" and they are prompted to "download an update". The link used for the supposed update download may appear as:

• http://94.249.92.28:7777/[...]/?ch=&ea=
• http://94.249.92.28:7777/[...]/flash_update.exe
  

Clicking the link will download and install the malware onto the system.

Execution

Upon execution, the malware will create these files:

• %windir%che07.exe
  copy of the malware file
• %windir%emark2.dat
  malware data file
• c:1.reg
  contains a routine to add entries to the registry
• c:64234543.bat
  the malware's cleanup routine

The malware will then add an entry to the registry so that it will be capable of inserting an HTML page into another HTML page, which can be useful when inserting comments in user pages inside networking sites.

• HKEY_CLASSES_ROOTMimeDatabaseContent Typeapplication/xhtml+xml
  "CLSID"="{25336920-03F9-11cf-8FD0-00AA00686F13}"
  "Extension"=".xml"
  "Encoding"=hex:08,00,00,00

It will also create a registry key

• HKCUSOFTWAREMicrosoftWindowsCurrentVersionExplorerAdvanced
  Hidden =

To create the message or comment it needs to propagate, the worm connects to a website that contains the necessary message contents and the malicious URL. It is able to connect to more than one website to do so.

The downloaded text strings and malicious links are combined to form the messages that the worm posts to all of the infected user's contacts on the social interaction site.

The malware also contains a routine to download and install files into the system, though the file in question was unavailable at the time of analysis.

Packer

The worm is packed by the UPX packer.

Last update 10 December 2008

 

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