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Microsoft has teamed up with Facebook to purge the persistent Koobface worm from the popular social-networking site.
Security researchers from Microsoft added detection for the Koobface worm to Microsoft's Software Removal Tool (MSRT) two weeks ago. In the intervening fortnight, more than 133,000 infected Windows PCs have been cleaned up as a result, Microsoft said in a posting on Facebook on Thursday.

Koobface is a worm that works by spamming the contacts of an infected user with messages, such as "Check out this video", directing them to a third-party site hosting malware. Prospective marks are invited to download an "audio code" to view the supposed video clip. This software update contains the malware payload, which activates if executed on a Windows machine, restarting the whole cycle of infection. The malware creates a backdoor on compromised machines, allowing the download of Trojans and other nasty under the control of hackers.

Variants of Koobface first surfaced last August. Multiple variants, some targeting MySpace and Bebo, have cropped up since and continue to be produced. Facebook outbreaks have occurred in August, December, and March, periodically though not particularly seriously - something like the electronic equivalent of herpes.
Microsoft's Software Removal Tool tackles over 100 strains of malware. It's partnership with Facebook shows its prepared to bring other firms on board in fighting the scourge of malware, which (for most intents and purposes) remains a Windows-only problem.


MS teams with Facebook to eradicate Koobface worm ? The Register