Microsoft was aware of a critical vulnerability in an Internet Explorer component at least 12 months before attackers started targeting it in lethal exploits that take full control of end-users' PCs, a member of its security team said Wednesday.
The disclosure comes as attacks targeting the MSVidCtl ActiveX control vulnerability have increased exponentially. On Monday, online ads distributed
by through the Giant Realm network on popular gaming websites began including code that exploits the bug, according to security firm ScanSafe. The ads mean that anyone using IE to browse sites such as diii.net and incgamers.com are risk if they run the XP or 2003 versions of Windows and have not yet installed a quick fix.
(A spokeswoman for Giant Realm said she was looking into ScanSafe's report. She didn't get back to us by time of publication).
The company didn't issue an advisory and temporary fix until Monday, a day after reports first surfaced that the vulnerability was being exploited in the wild. (To be fair, it took Apple until last month to fix a critical vulnerability in Mac versions of the Java virtual machine, six months after Windows versions were patched).
Mike Reavey, director of the Microsoft Security Response Center, said there are some very good reasons why the company waited so long, and one of the security researchers who discovered the bug concurs. More on that in a moment. But for others in the security industry, the delay is troubling because it may have given attackers a leg up.
"Whenever there is a zero day, the big concern is that other attackers will adopt it for their own purposes, and that's exactly what's happened here," Mary Landesman, senior security researcher at ScanSafe, told The Register. "And they were pretty quick to do it, because this was a day after the zero-day exploit became widely known."
Rogue ads on gaming sites are by no means the only place where the vulnerability is being exploited. Google searches such as this one suggest there may be close to 3 million compromised webpages that redirect users to a malicious site targeting the exploit. That's a massive increase from just a few days ago, when the number of compromised websites was believed to be in the thousands.
Microsoft's Reavey defended the decision to withhold an advisory until Monday, explaining that any fix must meet a demanding balancing act that ensures it is thorough enough to block a wide variety of related attacks while narrow enough that it doesn't cripple crucial parts of the software.
"Not every issue is the same as far as the level of work we need to do to be comprehensive in making sure we fix not just the issue reported to us but any similar issues," he said. "If we release an update that breaks apps it doesn't protect anybody because they won't install it."