Microsoft has reissued a Windows security patch that it published last week because the software did not work properly on Windows 2000 systems.
The October 10 patch did not correctly configure a Windows Registry setting called a 'kill bit', to prevent Windows 2000 from running software that could be attacked. Other versions of the operating system, including Windows XP and Windows Server 2003, are not affected by this problem, Microsoft said.
The patch, described in the MS06-061 security bulletin fixed problems in the Windows XML parser.
"The revised version we released today protects against all the vulnerabilities discussed in MS06-061 and correctly sets the kill bit," wrote Microsoft Security Program Manager, Ben Richeson, in a Thursday blog posting.
Microsoft, which is in the process of reorganising its security divisions, has had a few high-profile security gaffes over the past few months. In August, it was forced to reissue a critical security patch after researchers discovered that the software introduced a critical security bug.
And some Windows users had to wait for hours last Tuesday as Microsoft sorted out networking problems that kept the security patches from being properly copied between Microsoft's internal staging systems and those used by its customers.
This latest error is an embarrassing one for Microsoft, senior information security analyst at Cybertrust, Russ Cooper, said.
"They might as well have issued M&M's for Windows 2000 customers," he said via instant message. "How basic a task is it to ensure the patch does what they wrote in the bulletin? How poorly are their Q&A processes if such a problem can slip through?"
IDefense's Ken Dunham, however, was reluctant to criticise Microsoft for the error.
"Vulnerability patching and patch management is a very complicated process. Anybody who thinks it's a very simple process for large enterprises doesn't understand it," he said.