The critical bug that Microsoft confirmed but has yet to patch is a prime candidate for another Conficker-scale attack, a security researcher said.
“It's better than [the vulnerability used by] Conficker,” Roger Thompson, chief research officer at AVG Technologies, said. “It exposes the whole world, and can be exploited through the firewall. That's better than Conficker, which mostly did its damage once it got inside a network.”
Conficker, the worm that exploded into prominence last January when it infected millions of machines, exploited an already-patched bug in Windows that Microsoft had thought dire enough to fix outside its usual update schedule.
The worm hijacked a large number of PCs — estimates ranged as high as 12 million at one point — and then assembled them into a massive botnet able to spread malware, plant fake antivirus software or distribute huge amounts of spam.
“I have no doubt that the really bad guys are bustling to get this [new vulnerability] into their exploit toolkits,” said Thompson. “For the Conficker people, this could be the next thing. They waited until they had a really good exploit, then combined that with some smart strategies. So I wouldn't be surprised if they picked up on this.”
The vulnerability Thompson's worried about is in the Microsoft Video Controller ActiveX Library, or the “msvidctl.dll” file, an ActiveX control that can be accessed using Internet Explorer (IE). Although the bug has been used by hackers since at least June 9, it only made it into the public eye this week, when several security companies, including firms in both China and Denmark, reported that thousands of compromised sites were serving up exploits.
On Monday, Microsoft acknowledged the vulnerability in a security advisory, said it would produce a patch and provided an automated tool to disable the ActiveX control by setting nearly three-dozen “kill bits” in the Windows registry.
“This is a good exploit with a big lump of infectable people,” said Thompson.
One reason why the bug is an excellent choice for hackers is that it hasn't been patched. When Conficker first appeared, the flaw it exploited had already been patched by Microsoft. It turned out, however, that there were plenty of PCs that had not been updated with the fix.
Thompson wouldn't hazard a guess as to whether Microsoft would be able to craft a fix in time to add it to the patches slated for delivery next Tuesday, July's regularly-scheduled update day. “But I'm fairly confident that they're trying very hard,” he said.
Attack code is readily available, Thompson said, meaning that attackers not yet abusing the bug don't have to figure out an exploit of their own. “If the people who infect banner ads use this before there's a patch, then watch out,” he warned.
Microsoft admitted that researchers at IBM's ISS X-Force had reported the vulnerability in 2008, but did not name the date. The X-Force researchers had uncovered the flaw in late 2007, and had reserved a CVE (Common Vulnerabilities and Exposures) number in December of that year. One of the researchers, Alex Wheeler, who is now the manager of 3Com's TippingPoint DVLabs, declined to name the date ISS reported the bug to Microsoft, citing a non-disclosure agreement he'd signed with his former employee.
Microsoft didn't directly answer a question about why it had not patched the ActiveX vulnerability when it has known about the bug for at least six months and possibly as many as 18. “When we were alerted in 2008, we immediately started an investigation,” a company spokesman said today in an e-mail. “As we wanted to be thorough, this took extra time to fully evaluate.”
The “extra time” Microsoft needed may strike some as odd, since the ActiveX control — the “msvidctl.dll” file — is the company's own code. And that's unusual, said Thompson. “This is the first issue with a Microsoft .dll for, really, a long while,” Thompson said. “Maybe since the ANI bug in April 2007. Usually, it's a Chinese .dll or something from Adobe.”
The vulnerability in Windows' animated cursor — found in the “user32.dll” file — was patched more than 100 days after Microsoft was alerted by Alexander Sotirov, a vulnerability researcher at Determina. Microsoft issued an “out-of-band” patch for the ANI bug, breaking from its regular monthly schedule.
“It's not the end of the world or anything,” said Thompson. “But I won't be surprised to see Version 2.0 of Conficker with this. It seems custom-made for them.”
Systems running Windows XP or Windows Server 2003 are vulnerable to current attacks through IE6 and IE7. Windows Vista and Windows 7 are not at risk; nor are users running IE8 or other browsers, such as Mozilla's Firefox and Google's Chrome.