"Some users of the popular AOL Instant Messenger program were bombarded Wednesday with messages seemingly from friends that linked to a humorous Osama bin Laden game. Downloading the game, however, installed a piggybacking program that broadcast the advertisement from the infected computer to all correspondents on its AIM buddy lists.

"The program [called Buddylinks] is also clever in its use of social engineering to spread, extending a personal invitation that appears to come from what is typically a trusted friend," reports AP.

"In addition to being a particularly slimy form of adware, is also a violation of the AIM terms of service," said America Online spokesman Andrew Weinstein. "We are actively investigating what legal options we have to prevent this company from doing this."