Worm:Win32/Koobface.gen!F is generic detection for variants of Win32/Koobface, a multi-component family of malware used to compromise machines and direct them in various ways at the attacker's will. This could include using the affected machine to distribute additional malware, generate 'pay per click' advertising revenue, steal sensitive data, break captchas, and subvert the affected user's online experience. Its components are varied, but include a worm that spreads by utilizing social networking sites such as Facebook and MySpace.
If this worm is executed, Win32/Koobface copies itself to the Windows folder using a variable file name, as in the following examples:
The worm may drop a cleanup batch script file also variable file name to the root of the local drive, as in this example:
The worm may execute the cleanup batch script to remove the originally executed worm and to remove itself. The registry is modified to execute the dropped worm copy at each Windows start.
Adds value: <value>
With data: "%windir%/<worm file name>"
To subkey: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
MySpace and FaceBook Contacts
Win32/Koobface searches in the default Internet Explorer cookies folder for browser cookies related to the Internet social network sites including the following:
The worm spreads by sending messages containing a hyperlink to a copy of worm to friends or contacts of the infected user. Friends that receive the message may visit the link to download the worm and repeat the cycle of spreading to others.
Win32/Koobface can perform multiple payloads, depending on which components are installed on an affected machine. This can include:
downloading and executing arbitrary files, including additional malware
displaying pop-ups that attempt to intimidate affected users into installing rogue software
starting a webserver
starting a proxy server
Analysis by Scott Molenkamp