The problem affects the 'secdrv.sys' file, a component of the SafeDisc copy encryption developed by Macrovision and sold to game developers.
The DRM technology is bundled with Windows Server 2003, Windows XP and Windows Vista, but does not affect Windows Vista.
Danish security website Secunia rates the vulnerability as 'less critical', the second step on a five step severity scale. The risk to end users is limited because a successful exploit requires attackers to have an account on the targeted system.
Microsoft issued a security advisory on Monday in which it disclosed the ongoing attacks.
The company also linked to a patch that Macrovision has since issued, and said that Windows systems will be updated as part of the next Patch Tuesday update scheduled for 13 November.
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