The Ramnit worm has been spreading since April 2010, but was only recently adapted to target Facebook details, according to computer security experts. It was previously used by cyber criminals to steal login credentials for other services, including online banking.
I got hit by it a few weeks back, pain in the

At least it led me to test all the new software available to see what could remove it and pretty much everything failed apart from the following free applications:

Anti-virus - Mircosoft Security Essentials.... even pick these viruses up as you as you hit a page with them on and blocks them

Anti-Malware - Emsisoft... picked up more stuff on all my systems than any other software of this type.... and cured the Ramnit infection

For those with a real bad dose Dr Web is excellent, and free for home use, as it locks down your system while it scans.