Microsoft admits it knew of critical IE bug in early '08

and Wheeler worked when they discovered the vulnerability, said Monday that attacks had been recorded as early as June 11.

"We were made aware of the attacks the day before we released the advisory," Reavey said, which would mean the company knew of attacks on July 5, nearly a month after IBM said attacks had started. "Once we saw the attacks, we took a look at the current status [of our work] and what's being attacked, [and] put things on a fast track."

On a Microsoft blog today announcing the security updates slated for release next week, an MSRC spokesman said, "...our engineering teams have been working around the clock to produce an update."

Microsoft also denied that vulnerability details had leaked to hackers at some point during the last 16-18 months, perhaps through the Microsoft Active Protection Program (MAPP), a program that gives security software companies early information on bugs. "Microsoft did not share any information with MAPP partners about the reported Video ActiveX Control vulnerability until immediately before the advisory posted," a company spokesman said today.

Hackers are exploiting the ActiveX vulnerability by getting users to visit malicious sites, or planting drive-by attack code on legitimate sites. The number of compromised sites serving up the malware to IE6 and IE7 users has skyrocketed, and number in the millions, according to ScanSafe.

At some point, Microsoft will release a true patch for the problem, Reavey said. He declined to say whether that patch would be delivered "out-of-cycle" -- outside the normal monthly update schedule -- when it is ready, however.