Microsoft has joined the growing group of security software vendors who see Sony BMG's controversial XCP (Extended Copy Protection) copy protection software as a security threat.

On Saturday, Microsoft announced that it would begin treating the software as spyware and offering users tools to remove it.

"We have analysed this software, and have determined that in order to help protect our customers we will add a detection and removal signature for the rootkit component of the XCP software to the Windows AntiSpyware beta," wrote Jason Garms, group program manager for Microsoft's Anti-Malware Technology Team.

Sony has faced stinging criticism for its "rootkit" cloaking technologies - which uses techniques also used by hackers - to make CDs from the company an almost undetectable security threat to music fans.

After nearly two weeks of consumer backlash, however, Sony announced on Friday that it would temporarily suspend production of XCP-enabled CDs.

In a future weekly software update Microsoft will add the new electronic signature so that Windows AntiSpyware can spot and automatically remove the software, Garms wrote.

Microsoft will also include the XCP signature in the next update to its Malicious Software Removal tool.

Computer experts had worried that hackers might use XCP's cloaking capabilities to hide malicious software of their own, and last week the first few examples of such programs began surfacing.

More fun to come

Meanwhile, a Princeton University computer scientist has posted an analysis of a second copy protection product used by Sony, saying that it, too, suffers from many of the same problems as XCP. That software, called MediaMax, was written by SunnComm International. Sony has confirmed that it ships CDs with both SunnComm's software and XCP.

Both copy protection products are bad for consumers, according to Princeton science student Alex Halderman: "Like XCP, recent versions of MediaMax engage in spyware-style behavior," he wrote.

Halderman reported that MediaMax automatically installed files without user consent, that its uninstaller program does not completely remove the software, and that it secretly transmits user information back to SunnComm's servers.

"Playing First 4 Internet or SunnComm disks means not only installing new software, but trusting that software with full control of your computer," Halderman wrote. "After last week's revelations about the Sony rootkit, that trust does not seem well deserved."

This is not the first time Halderman has had something to say about SunnComm. In 2003, SunnComm threatened the computer scientist with a lawsuit after he published a paper that exposed weaknesses in their copy-protection mechanism. No legal action was ever brought against Halderman, according to SunnComm.

Sony, First 4 Internet and SunnComm Monday were unable to comment for the story.