Microsoft has sued an anonymous computer hacker whose free program allows users to copy digital movies and songs by bypassing a software protection built into the company's Media player.

The world's biggest software maker charges the hacker known as "Viodentia" has illegally obtained propriety source code to produce the program called FairUse4WM, sparking fears it could enable consumers to illegally copy digital content.

The program's name is a reference to legal rulings in which courts recognize "fair use" as the ability for consumers to copy recordings for personal use. Some consumer advocates argue that the digital media industry is ignoring that right in its attempt to stop illegal duplication.

The lawsuit marks the company's latest attempt to stop the programmer, who has repeatedly released updates to the program in response to Microsoft patches aimed at stopping the tool that strips away digital management rights code.

The lawsuit seeks a permanent injunction as well as unspecified compensatory and punitive damages.

"This software program enables users to alter or remove Microsoft's DRM from Windows Media files (i.e. it allows users to wrongfully access or copy a copyrighted music or movie file," the company said in its lawsuit filed in U.S. District Use in Seattle.

But a person using the identity Viodentia said in a Web posting the program has never involved Microsoft source code. The programmer also said in an online interview with Engadget that the lawsuit was a "fishing expedition to get identity information" in a bid to bring more lawsuits.

Allonn Levy, an attorney specializing in intellectual property on the Internet, said the program also highlights major problem facing content providers and software makers such as Microsoft as consumer demand grows for Web delivery of content such as movies and music.