The Redmond, Wash., software maker did not say when it would deploy the fix that counters the FairUse4WM application.
"We have an update to address the circumvention and are working with our partners to deploy this solution," Marcus Matthias, senior product manager for the Windows Client Division, said in an e-mailed statement.
Those partners include providers of music and video that depend on Microsoft's digital rights management technology to prevent illegal copying of their content. FairUse4WM, released anonymously on the Web more than a week ago, provides a graphical user interface for the DRM removal program called "drmdbg," simplifying the process of running files through the application.
The new tool works only on music files containing DRM technology from versions 10 and 11 of Windows Media player. The application can only work on one file at a time.
Microsoft has said for quite awhile that no DRM system is ironclad, and acknowledges that hackers can sometimes find a way around the protections in Windows Media Player. The technology, however, is flexible and can be tweaked relatively quickly to stymie attackers.
"We designed the Windows Media DRM system to be renewable, so that if such events occur the system can be refreshed to address them," Matthias said. "End users are not at risk due to this circumvention. This circumvention is against WM DRM content."
FairUse4WM is unique because it could be used to free tunes downloaded on PCs through Windows Media-supported subscription services, such as those offered by Yahoo and Napster. Once the DRM is removed, the files, for example, could be played on Apple Computer's Macs or iPod portable media players.
Subscription services store music on a PC, so it can be moved to a portable device. The DRM application prevents the music from being copied to a CD, and contains a 30-day timer that resets every time the subscription is renewed. No renewal and the files deactivate.
The release of FairUse4WM sparked fair-use debates on some tech Web sites. In an open letter to Microsoft, Engadget editors called on Microsoft not to patch the DRM, arguing that restrictions on music use drives more people to illegal download sites.