The flaw, revealed late last week, has been exploited in limited attacks, according to the Microsoft.
"While we don’t have a firm estimate on when we’ll complete our development and testing of updates for the issue, we have teams around the world working on it 24 hours a day, and hope to have updates no later than May 8 for the May monthly bulletin release," Christopher Budd, Microsoft security program manager, said on the company’s Security Response Center blog on Tuesday.
"However, this is a developing situation, and we are constantly evaluating the situation and the status of our development and testing of updates."
Budd added that Microsoft must test and develop 133 separate updates — one for every language for which the company produces software. He also urged administrators to employ recommended workarounds.
Minoo Hamilton, senior vulnerability researcher at nCircle, told SCMagazine.com that DNS issues affect every user browsing websites on affected servers, so Microsoft must be extremely cautious to ensure the patch is not more harmful than the flaw.
"I think that the timing of the patches has partly to do with how severe [the flaw] is, but also how quickly they can get it done and tested. Because it’s in DNS, it affects a lot more than just that server," he said. "So they might have to use a lot more caution with this patch."
On Tuesday, researchers reported that variants of the Rinbot worm (also known as Delbot and Nirbot) had attacked the flaw.
Microsoft updated its advisory on Monday, reporting that new attacks were actively exploiting the vulnerability.
Researchers told SCMagazine.com this week that the worm is flexible enough to attack vulnerabilities other than the DNS flaw, possibly resulting in the redirection of users to malicious websites.
Symptoms of infection by the variant include unexpected HTTP traffic over non-standard ports and unusual DNS queries, according to McAfee researchers.
Exploits were first publicly released for the DNS flaw on Sunday.
Hamilton said the workarounds recommended by Microsoft may be difficult for administrators to employ.
"The workaround is pretty tough for DNS admins because they use these tools to manage their systems, so it can be pretty difficult to prevent RPC access," he said. "Admins rely on these administration tools that use that interface, so it can be a major inconvenience to implement."
Microsoft works against the clock to ready DNS fix
By Frank Washkuch on Apr 20, 2007 9:49AM