Microsoft was first alerted to the .ANI vulnerability back in December, but a patch for it didn't come before exploits began hitting the wild last week.
Mark Miller, director of the Microsoft Security Response Center, said in an interview Monday with InformationWeek that the company needed the three-plus months to work on building and testing a good patch. Since the exploit hit last week, he said slightly less than 100 Microsoft technicians have been working "around the clock" to ready the patch.
A security researcher at Determina, a security company based in Redwood City, Calif., reported the vulnerability to Microsoft on Dec. 20, according to Miller. Working with Determina, Microsoft researchers, including program manager Adrian Stone, immediately began investigating the bug. A patch for it was going to be released April 10, as part of Microsoft's monthly Patch Tuesday update, but the fix release has been pushed up a week to deal with the growing number of malicious sites and other threats that are popping up to take advantage of it.
Miller stands behind Microsoft's response process and said it has taken the company more than three months to come up with a patch for the bug because it's simply a long, complicated process.
"It just took the time it took to produce this update," he said. "When you look at the time it takes to review the security issues, create a fix, and then test, it does take some time. ... Where it is in Windows, it is a core area. The time line is longer because you have to deal with this core area."
Miller would not say exactly where the flawed code is because he doesn't want that information out before customers can patch their systems.
The .ANI vulnerability lies in the way Windows handles malformed animated cursor files and could enable a hacker to remotely take control of an infected system. The bug affects all the recent Windows releases, including its highly touted Vista operating system. Internet Explorer is the main attack vector for the exploits.
Users are being infected after visiting a malicious Web page that has embedded malware designed to take advantage of the flaw. They also can be infected if they open a specially crafted e-mail message or if they open a malicious e-mail attachment sent by a hacker. Websense, a security company, reported that it has found more than 100 malicious Web sites that are exploiting the vulnerability.