PC-pwning infection hits 30,000 legit websites

And counting

By Dan Goodin

Posted in Security, 30th May 2009 00:21 GMT

A nasty infection that attempts to install a potent malware cocktail on the machines of end users has spread to about 30,000 websites run by businesses, government agencies and other organizations, researchers warned Friday.

The infection sneaks malicious javascript onto the front page of websites, most likely by exploiting a common application that leads to a SQL injection, said Stephan Chenette, manager for security research at security firm Websense. The injected code is designed to look like a Google Analytics script, and it uses obfuscated javascript, so it is hard to spot.

The malicious payload silently redirects visitors of infected sites to servers that analyze the end-user PC. Based on the results, it attempts to exploit one or more of about 10 different unpatched vulnerabilities on the visitor's machine. If none exist, the webserver delivers a popup window that claims the PC is infected in an attempt to trick the person into installing rogue anti-virus software.

The rogue anti-virus software uses polymorphic techniques to constantly alter its digital signature, allowing it to evade detection by the vast majority of legitimate anti-virus programs. Because it uses obfuscation, the javascript is also hard to detect by antivirus programs and impossible to spot using Google searches that scour the web for a common string or variable.

"For the common user, it's going to be possible but difficult to determine what the code is doing or if it's indeed malicious," Chenette told The Register. "We can see this quickly growing."

The infection shares many similarities with a mass website malady that's been dubbed Gumblar. It too injects obfuscated javascript into legitimate websites in an attempt to attack visitors. So far, it's spread to about 60,000 sites, Websense estimates.

Several differences in the way the javascript behaves, however, have led Websense researchers to believe the two attacks are unrelated.

The researchers have also noticed that the code, once it's deobfuscated, points to web addresses that are misspellings of legitimate Google Analytics domains that many sites use to track visitor statistics. The RBN, or Russian Business Network, has used similar tactics in the past, and Websense is now working to determine whether those responsible for this latest attack have ties to that criminal outfit.

"It could be that the RBN is related, or more likely because that code was publicized, the attackers are acting in a very smart fashion to duplicate methods of old attacks to hide their tracks," Chenette explained.

Websense, which scans millions of websites each hour, has issued a preliminary advisory here. It plans to issue additional details on Monday. ®

http://www.theregister.co.uk/2009/05/30/mass_web_infection/