Just days after the release of Microsoft's latest security patches, security researchers have begun publishing software that could be used to seize control of unpatched Windows-based computers.

Microsoft released a total of six patches last Tuesday as part of its monthly security bulletin. Of the three critical flaws that were attended to, security experts are particularly concerned about 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.

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.

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

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

Adding to Microsoft's disappointment was the fact that the IE patch was released late for some users. The company released a corrupted version of its MS05-038 patch on Tuesday, which meant that users who picked up the patch from Microsoft's Download Center within the first few hours of its release were unable to install the software.

Microsoft pulled that patch from the Download Center on Tuesday and had a working version available the next day. Software on Windows Update, Microsoft Update and the Windows catalogue was unaffected by the glitch, Microsoft said.