IE Exploit Strikes, Installs Spyware

vulnerability Web site spyware

"We just received a report that a particular site uses the vulnerability to install a spybot variant," the SANS Institute's Internet Storm Center (ISC) warned Friday in an alert. "It is a minor site with insignificant visitor numbers according to Netcraft's 'Site rank.'"

Disclosed only Wednesday, the flaw in IE 5.01, 6.0, and the January version of IE 7 Beta 2 Preview has security vendors worried because a patch isn't available from Microsoft. Thursday, as news circulated that a working exploit had been publicly posted, Microsoft said it was working on a fix.

Even before the site exploiting the CreateTextRange bug was discovered, security companies had raised alarms. The ISC bumped up its InfoCON level to "yellow" for the first time since the Windows Metafile fiasco in late December, when another "zero-day" flaw hit Windows users.

"It's a relatively trivial mod[ification] to turn [the exploit] into something more destructive," the ISC warned. "For that reason, we're raising Infocon to yellow for the next 24 hours."

Symantec raised its ThreatCon status indicator to "2" and boosted its Internet Threat Meter's warning for Web activities to "medium" because of the bug.

Although it's unclear exactly whether the Spybot-distributing site is drawing users to its poison or simply waiting for the unwary to stumble across the URL, it's likely the former, Scott Carpenter, director of security at Secure Elements, said in an e-mail to TechWeb. "The most probable vector for this worm will be in the form of spam with malicious links that will tempt users into clicking on a link that takes them to a malicious site."

In December (and after), hundreds of sites used the Windows Metafile bug to load spyware, including keyloggers and backdoor Trojans, onto unsuspecting users' PCs.

Rumors that Microsoft would release a patch before April 11, the next regularly-scheduled patch day -- such releases are dubbed "out-of-cycle" -- was quashed by a Microsoft spokesman who refused to commit the company to a date.

"Upon completion of this investigation, Microsoft will take appropriate action to help protect our customers," he said in a verbatim repeat of Thursday's advisory. "This will either take the form of a security update through our monthly release process or providing an out-of-cycle security update, depending on customer needs."

So, what should users expect, say, over the weekend and early next week?

"It's hard to say at the moment, since this is just the beginning," said Alain Sergile, a technical product manager at Internet Security Systems' X-Force research. "But if SANS' report is accurate, I think we'll see additional targeted attacks where spam is sent to users at a specific organization in the hope that someone clicks on the link and downloads the malicious code so the attacker can infiltrate the network."

Because it remains an unpatched vulnerability, "everyone should consider this a zero-day kind of threat," added Sergile. "That means people will be caught flat footed."

Microsoft has recommended that users disable Active Scripting in IE until a patch is posted, but Sergile said that wasn't really a workable solution. "That will kill the capability of a large number of Web sites. The Web isn't much fun without those [scripting] capabilities." Instead, he recommended users visit only sites they know are safe.

Or turn to another browser. "The problem is in how Internet Explorer interprets the scripting call. Firefox doesn't have this problem."