Just days after the release of the latest security patches, exploit software that could be used to seize control of unpatched Windows computers has appeared.

Microsoft released a total of six patches on Tuesday last week as part of its monthly security bulletin. Of the three critical flaws that were fixed, security experts are particularly concerned with one that affects the Windows Plug and Play system.

A total of three exploits for this vulnerability have now been published on the Fr-SIRT (French Security Incident Response Team) website, and while Microsoft is not aware of any attacks that use this code, Windows 2000 systems that have not been updated with Microsoft's latest patches are at "great risk," according to Marc Maiffret, chief hacking officer at eEye Digital Security.

A researcher who works for the company that first reported the vulnerability to Microsoft believes it is only a matter of time before attackers exploit it. "There are so many instances of exploit code out there, it's very easy to just drag and drop this worm into any of the virus-making toolkits and create your own custom attack," said Gunter Ollmann, Director of Internet Security System's X-Force research team.

Although the plug and play vulnerability, outlined in Microsoft security bulletin MS05-39 is now easily exploited on Windows 2000, an attacker would need to have a valid login to the system to take advantage of it on Windows XP or Windows Server 2003, Ollmann said.

Exploit code has also been published for a critical flaw in Internet Explorer and a less serious bug in Microsoft's Remote Desktop Protocol (RDP), both of which were patched on Tuesday.

The IE exploits would allow attackers to gain control of an unpatched system, while the RDP exploit simply crashes the affected system, Maiffret said. "If you have RDP open to the outside world, there's the potential that somebody can (launch a) denial of service," he said, "but you're not executing code."

In a statement, Microsoft said it was "disappointed" that security researchers had decided to release vulnerability code so close to the monthly patch releases.