If you never heard of this worm before, this is how it works:
1. Users on infected computer uses Facebook.
2. Koobface then deliver a fake message to the user's Facebook friends.
3. The message contains a link that points to a external website, who would prompt the visitors to download a file that claims to be an update for Adobe Flash player.
4. Once the file is downloaded and executed, the Koobface worm will then infects the said PC.
5. The cycle repeats.
Apart from self-distributing itself, the worm would also take over the PC's search engine use and reroute it to contaminated websites. It would also download a number of malwares that are able to block user's access to certain security website and leave the system's back door open for attackers to take control.
To add to the danger, Koobface also has a number of variants that are designed to attack other social networking sites as well such as MySpace, Twitter, Friendster and many more. So, for all social network addicts out there, do make sure that your security software are always up-to-date and be suspicious when presented with unknown links; even it comes from a trusted friend.
Remember, prevention is better than cure.