As Microsoft patched the Internet Explorer (IE) vulnerability that was used to break into Google's network, it also acknowledged that it had known of the bug since August 2009, when an Israeli security company reported the flaw.

"As part of [our] investigation, we also determined that the vulnerability was the same as a vulnerability responsibly reported to us and confirmed in early September," said Jerry Bryant, a senior program manager with the Microsoft Security Response Center, on the MSRC blog today.

The MS10-002 bulletin that accompanied the IE update credited Meron Sellem of BugSec for reporting the bug that has raised a ruckus since Google accused Chinese cybercriminals with hacking its network.

Sellem said that BugSec, a penetration testing and security firm in Rishon LeZion, Israel, reported the vulnerability to Microsoft on Aug. 26, not in September as Microsoft indicated. And he was critical of Microsoft for taking this long to release a patch. "I think yes, it took too long," he said. "But Microsoft is a big organization and we don't know how much time it takes them. We asked them why it was taking such a long time, and they said it was because of the testing they had to do."

Andrew Storms, director of security operations at nCircle Network Security, said the fact that Microsoft knew of the vulnerability months before it crafted a patch -- months before Chinese criminals used the flaw -- shouldn't come as a shock.

"It's pretty par for the course, really," said Storms. "We know that patches sit for a good month or so in QA [quality assurance] at Microsoft. So if it was reported to Microsoft in September, it might not have been added to the [patch] cycle until October, and the code not written until November. A February release isn't crazy then."

Storms refused to use hindsight to say that Microsoft was tardy to the party. "Unless you have real evidence that it's being used, you can't take that into account when you prioritize patches," he argued. "You take into account the skill level necessary to exploit it. But if it's responsibly disclosed, you have to assume that it's not going to release [publicly]. And without partners saying that they're seeing signs of it being exploited, Microsoft probably thought they could just roll it into their normal IE release cycle."

Microsoft last patched IE in December 2009, and on average, updated its browser every two months.

It didn't surprise Sellem that others found the vulnerability, then decided to use it maliciously. "We found this vulnerability very easily," said Sellem, "and we didn't think it would be hard for others to find." BugSec spent about two weeks researching IE before it discovered the flaw, Sellem added.

"There have certainly been cases when multiple people have reported the same bug, so it's not hard to fathom that more than one could have found this at around the same time," said Storms.

Besides the patch for the vulnerability used to attack Google and others, Microsoft also patched seven other bugs in IE in today's update. Of the eight flaws fixed today, seven were rated "critical" by Microsoft, the highest threat ranking in its four-step scoring system.