Original URL: http://www.theregister.co.uk/2005/11/10/sony_drm_unmasked/

Sophos develops Sony DRM unmasking tool

Unplugging Sony's Root-man

By John Leyden

Posted in Security, 10th November 2005 17:29 GMT

UK security firm Sophos plans to release a tool which will detect the existence of Sony's DRM copy-protection rootkit on Windows computers, disable it, and prevent it from re-installing.

The move follows the discovery of the first malware (a Trojan called Breplibot) that takes advantage of Sony-BMG's use of rootkit technology in DRM software bundled with its music CDs to mask its presence on infected systems.

"Sophos is acting on customers' concern that the software on Sony's CDs is introducing a vulnerability which hackers and virus writers are able to exploit," explained Cluley. "We will give customers the ability to determine if their computers suffer from the vulnerability and remove it if necessary." The free download should be available today.

Sony-BMG's rootkit DRM technology masks files whose filenames start with "$sys$". A newly-discovered variant of of the Breplibot Trojan takes advantage of this to drop the file "$sys$drv.exe" in the Windows system directory. Once loaded in this way the malware will be invisible to anti-virus scanners. Only rootkit scanners, such as the free utility RootkitRevealer, can unmask the malware.

Sophos's tool will remove this cloaking behaviour but will not remove the software components installed by Sony-BMG, the deletion of which might cause system instability. But this very cloaking means it may not be obvious to users that they need the tool. Around 20 CDs from Sony-BMG which have shipped an estimated 2m copies around the world feature the controversial DRM technology, developed by UK security developer First4Internet. Sophos obtained advice from First4Internet in developing its tool.

We wanted to ask First4Internet and Sony-BMG what they intended to do to make sure their copy-protection technology wasn't abused by virus writers but neither returned our calls this afternoon. ®