Microsoft has denied that an anti-piracy "feature" in its Windows Media Player that allows a Trojan horse to run on a user's PC is a vulnerability.
Panda Software warned earlier this week that hackers are using the player's DRM tool to fool people into downloading spyware and viruses.
The Spanish security company said that virus writers had released licence-protected multimedia files containing Trojan horses (WmvDownloader.A and WmvDownloader.B) that can exploit the anti-piracy features in version 10 of the Media Player and Windows XP SP2.
Despite Panda's warning that the Trojan can download a cocktail of malware, Microsoft denies there is a flaw in its software.
"This Trojan appears to utilise a function of the Windows Media DRM designed to enable licence delivery scenarios as part of a social engineering attack," said Microsoft in an emailed statement.
"There is no way to automatically force the user to run the malicious software. This function is not a security vulnerability in Windows Media Player or DRM."
But Microsoft didn't say whether Windows XP SP2 fully protected users from unwanted downloads.
"Internet Explorer for Windows XP SP2 helps prevent downloads from automatically launching. Users who have installed Windows XP SP2 and turned on the pop-up blocker have an added layer of defence from this Trojan's attempt to deliver malicious software," said Microsoft.
The Redmond giant also said that people should go to the police if they think they have been attacked by such Trojans.
Microsoft also added that "customers in the United States who believe they have been attacked should contact their local FBI office or post their complaint on www.ifccfbi.gov. Customers outside the US should contact the national law enforcement agency in their country."