Adware Spreads Quickly on AOL IM

The problem starts when users receive an instant message that appears to come from someone on their Buddy List (a list of friends and co-workers who also use the AOL Instant Messenger service). The message reads "check this out" and includes a link that contains a reference to "osama capture.php."

If users click on the link, a program that is supposedly a game asks permission to be downloaded and installed onto their computers. Installing the game gives the company that produces it -- purportedly, an outfit called PSD Tools -- permission to display ads on the users' computers. In addition, the software spreads the "fun links" to everyone on the users' Buddy Lists.

"While many who have installed it are describing the game as a virus, the truth is that by neglecting to read the terms of service included with the game, they have given the program's distributors permission to take over their computers," said Matty Janko, a systems administrator whose 23-computer network was invaded by the game Wednesday.