A friend on Facebook suggests that you watch an amazing or funny or sexy video. The link may seem innocuous enough. But with a few simple clicks, you could end up infecting your PC with the Koobface worm.
Koobface, whose name is an anagram for its preferred social network, is a malicious program that has plagued Facebook for more than two years, ensnaring hundreds of thousands of people and keeping the site's security team on the defense.
The worm was Facebook's first major security challenge and remains the most persistent threat on the site. As such, Koobface has played a big role in shaping Facebook's approach to combating malicious software, or malware, and propelled the development of increasingly elaborate defenses.
Yet the worm continues to be a thorn in the side of Facebook's in-house investigators, who say they are on the trail of the organized criminal group that created it but, so far, have been denied the satisfaction of arrests.