Worm Morphs, Attacks Banks With Zeus-Like Features

Banks in the U.S. and U.K. are under attack by a newly retooled worm that incorporates features from the infamous Zeus and SpyEye financial fraud Trojans.

Ayelet Heyman, senior malware researcher for Trusteer, calls the so-called Ramnit "a powerful weapon." The Ramnit malware has been around for about 18 months, and was recently discovered sporting Zeus-like capabilities, such as HTML code injection into browsers in order to game two-factor authentication and transaction signing systems used by financial firms for online banking security.

"The strength of Ramnit is in its parasitic behavior -- in its spreading speed and infection scale," Heyman says. "Usage of a worm like Ramnit, which is known for its large infection scale, as a platform to commit financial fraud creates a powerful weapon."

Ramnit represents some 17.3 percent of all new malware infections, according to recent Symantec data, and Trusteer says it found tens of thousands of machines are infected with Ramnit. The malware's command-and-control servers are still up and running, residing in Germany, according to Trusteer.

Initially a traditional worm that targets .exe, .scr., .dll, and .html file types, as well as others, Ramnit has adopted some Zeus features, thanks to the source code for the infamous malware platform becoming available online this year. Trusteer researchers say it's easy to move Zeus to Ramnit because the technique for configuring Ramnit to go after a particular bank is the same as doing so with Zeus.

Ramnit's man-in-the-browser (MitB) Web injection module lets it modify client-side Web pages as well as transactions in such a way that's invisible to the user and host application, Heyman says.

"The metamorphosis of Ramnit into financial malware is a sign of things to come now that the Zeus source code has been made openly available to anyone on the Internet," says Amit Klein, CTO of Trusteer. "Unlike the past, when financial institutions had to defend against a limited number of malware platforms, attacks can now come from virtually any malicious software program -- old or new. The malware distribution channel for fraudsters has increased in scale significantly."

Trusteer included screen shots of the Ramnit attacks in a blog post today.

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