Earlier this week, security companies warned that attack code for exploiting the flaw was circulating on the Internet. On Thursday, Sunbelt Software said it had found a Web site hosting a malicious Winamp playlist file. Opening the file loads spyware onto an unwitting user's PC, it said.
"After surfing to a malicious Web site on our test machines, the file 'x.pls' begins to download," Sunbelt's Adam Thomas wrote in a posting on the anti-spyware software maker's corporate blog. "Almost immediately, Winamp starts to execute the play list and remote code execution begins."
The flaw was an update to fix it. The company posted version 5.13 of Winamp, while Secunia and other security companies issued alerts about the problem. Secunia rated the issue "extremely critical," its highest rating., when Winamp maker Nullsoft, a division of America Online, released
"Not following the recommendation from Nullsoft to upgrade to version 5.13 could result in the extremely nasty CWS Looking-For.Home Search Assistant infection as well as an installation of our good friend SpySheriff," Thomas wrote. Antivirus software is not yet detecting this exploit, he wrote.
Home Search Assistant might monitor a user's activity and send out confidential information to its creator, according to Sunbelt's threat database. SpySheriff will display a false warning that the computer is infected with spyware. It then tries to persuade the user to buy a SpySheriff product, according to Sunbelt.
Distributors of adware and spyware oftento get their applications onto PCs. Makers of such software often pay distributors per installation of the adware or spyware.
The Winamp problem affects version 5.12 of the media player. Earlier versions may also be affected. On Friday, the malicious Web site referred to by Sunbelt, 008k.com, appeared to be offline. The site displayed a message: "Site is closed for abuses."