Threat Descriptons



Category :


Type :


Aliases :

Net-Worm:W32/Koobface.CZ, W32/Koobface.worm (McAfee)


This worm attempts to spread via messages or comments containing malicious links, which are posted on social networking websites.


Based on the settings of your F-Secure security product, it will either move the file to the quarantine where it cannot spread or cause harm, or remove it.

A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:

  • Check for the latest database updates

    First check if your F-Secure security program is using the latest updates, then try scanning the file again.

  • Submit a sample

    After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.

    Note: If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.

  • Exclude a file from further scanning

    If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.

    Note: You need administrative rights to change the settings.

Technical Details

Websites referenced in the worm's code are:


Though the Koobface family is most commonly associated with Facebook and MySpace, the routines in this particular Koobface variant target and are not specifically intended for the other websites.


The worm spreads by posting a message containing a link to a malicious website on all of an infected user's site contacts. The messages or comments posted 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 also vary and may appear as:


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


This malicious website masquerades as a YouTube webpage. The user is 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:


Clicking the link will download and install malware onto the system. The downloaded malware is detected as Net-Worm:W32/Koobface.CY.


Upon execution, the downloaded malware will create these files:

  • %windir%\che07.exe - Copy of the malware file
  • %windir%\bemark2.dat - Malware's 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_ROOT\Mime\Database\Content Type\application/xhtml+xml "CLSID"="{25336920-03F9-11cf-8FD0-00AA00686F13}" "Extension"=".xml" "Encoding"=hex:08,00,00,00

It will also create a registry key

  • HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced 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.


The worm is packed by the UPX packer.

Process Changes

Creates these mutexes:

  • 44455345g43545

Network Connections

Attempts to connect with HTTP to:

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