The fake anti-virus attack first appears in your timeline as a message apparently posted by one of your friends.
In case you've been out of the loop, the text used refers to the news story of IMF chief Dominique Strauss-Kahn who is facing charges in New York over charges that he allegedly tried to rape a hotel maid.
People who know what they're doing will recognize this for what it is - a sick fakey headline and the promise of a video is used to entice people to click on the link which goes to a site pushing malware - in this case Mac Defender. For good measure clicking on the link also posts the same message onto the Facebook wall of the person clicking on the link - this helps find the next sucker victim.
Sophos senior technology consultant Graham Cluley calls it a 'a genius piece of social engineering.'
Needless to say, if you see this on Facebook, don't click on the link!