Microsoft announced on Monday that customers using Windows 2003 and Windows XP have reported attacks exploiting a previously unknown vulnerability in a component of the operating system that implements Macrovision copy protection.

The flaw, which occurs in the secdrv.sys driver, could allow malicious code to elevate its privileges on the target machine, Microsoft stated in its advisory. Macrovision offered a patch for the problem on its site, and Microsoft plans to push the patch out to customers using its automatic update service after it has tested the patch.

"We are aware of limited attacks that try to use the reported vulnerability," the company said in an advisory. "Microsoft is actively monitoring this situation to keep customers informed and to provide customer guidance as necessary."

Online attackers have increasingly targeted flaws in third-party applications that run on the Microsoft Windows rather than finding vulnerabilities in the operating system itself. Last week, security firms warned that fraudsters had started using malicious Portable Document Format (PDF) files in an attempt to compromise victims' systems. While the attack used PDF documents and Adobe's Acrobat Reader, the actual flaw is in the Windows operating system, Microsoft said last week.

The latest vulnerability, which is in the third-party Macrovision driver that ships with Windows XP and 2003, does not affect Windows Vista, according to Microsoft.

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