Microsoft has posted an update to Windows Media Player, its flagship audio/video application, to stymie attacks by Trojan horses intent on planting spyware on users' machines.

In January, security firms noted that several Trojan horses were spoofing Digital Rights Management (DRM) licenses, and were downloading massive amounts of spyware, adware, and other malicious code to PCs.

The Redmond, Wash.-based developer said that the update, which installs two components, "improves the robustness of the Windows Media DRM platform and adds additional integrity checks to the DRM system."

The modifications to Media Player will also allow DRM license issuers to verify that each user's PC has been updated to the newest edition of the application before they issue new licenses or renew existing ones, Microsoft added.

The update can be downloaded from Microsoft's Web site.