Nobody knows how widespread this malware really is, but when Koobface first appeared on the scene, Facebook said it was affecting less than 0.02 percent of users. Facebook boasts more than 110 million users; 0.002 percent of that would represent 220,000 users.

Security experts have long warned that the Web 2.0 mash-up model of allowing users to put together their own content from many different sources naturally creates many security problems. In part, this is because it allows anyone to post material on trustworthy domains such as Google.com.

"I believe that you will see more of this stuff happening," said Petko Petkov, a security researcher with GNUCitizen.

With corporate Intranets adopting new technologies such as blogging and Wikis, Petkov thinks corporate targets may soon be ripe for attack. "If you have a worm inside a corporation that works the same way as the worm on Facebook, you have a huge problem."