The vulnerability affects the Workstation Service in Windows 2000, which handles print and file requests.
Microsoft has already created a patch for the problem but the exploit code has taken just two days to appear on the internet and could hit unpatched systems.
"Microsoft has patched 13 vulnerabilities this month and among them is one that can be used to create a worm targeting Windows 2000 systems," said a statement from antivirus vendor McAfee.
"The MS06-070 Workstation Service vulnerability can be remotely exploited without user interaction. On Windows 2000, no authentication is needed when sending traffic to this service."
McAfee warned that adding the ability to replicate the software could lead to an attack similar to the Zotob worm.
In that instance, Zotob appeared just a few days after Microsoft had patched a similar problem.
Exploit code adds to Windows 2000 threat
By Matt Chapman on Nov 20, 2006 9:52AM
Code that exploits a critical flaw in Windows 2000 to access systems has been released onto the internet, raising the possibility of a widescale worm attack.
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