Zeus Banking Malware Gets 64-Bit Facelift

Bad news on the financial malware front: The Zeus banking Trojan has gotten a major upgrade, gaining some compatibility with 64-bit versions of Windows.

"What's the most notorious banking malware? Zeus, of course -- the trendsetter for the majority of today's banking malware," said Kaspersky Lab information security researcher Dmitry Tarakanov in a blog post. "Its web injects have become a fundamental must-have feature of almost every banking malware family. And it was only a matter of time until a 64-bit version of Zeus appeared -- but we didn't expect it to happen quite so soon."

The Zeus banking malware won't seem to die, even after its creator claimed in 2010 that he planned to retire. Last year, related infections declined, only for Zeus infections to resurge in the first half of this year. According to a sample just discovered by Kaspersky, a 64-bit version of Zeus debuted on April 29, 2013.

At the moment, however, such capabilities are overkill, given that only 0.01% of all Internet Explorer users are using a 64-bit version of the browser. "Cybercriminals don't actually need a 64-bit version," Tarakanov said. "Zeus is mostly intended to intercept data passing through browsers, and modify that data allowing the operator to steal information related to online banking, to wire transactions, or to cover his tracks. But nowadays people still use 32-bit browsers -- even on 64-bit operating systems. So, 32-bit versions of Zeus have been sufficient to keep the thieves satisfied with their earnings."

[Prosecutors have a new tool in their arsenal. See Cybercrime Milestone: Guilty Plea In RICO Case.]

As of nine months ago, the 64-bit capabilities appeared to be a work in progress. That's because, due to an API error, the 64-bit functionality -- which is contained inside a 32-bit version of Zeus -- caused the related process to crash. But as more people migrate to 64-bit systems and browsers, whoever is developing Zeus appears to be planning to keep up.

The most recently spotted version of Zeus also continues its support for the Tor anonymizing network, which is designed to hide people's Web browsing activity and disguise who's communicating via whom on the Internet. Zeus isn't alone in this respect, since a number of other types of malware -- including TorRAT and the recently spotted i2Ninja Trojan -- have embraced Tor as a way to obscure both the botnet's command-and-control mechanisms, as well as related data exfiltration activities.

The Zeus upgrades suggest that the crimeware toolkit developer has a healthy, well paying customer base. According to the Zeus tracker, which keeps tabs on Zbots, as of Thursday 723 Zeus command and control (C&C) servers were being tracked, and 361 were online. In addition, the Zeus malware used to infect targeted PCs -- phishing attacks remain a popular attack vector -- was spotted by antivirus engines, on average, only 39% of the time.

Zeus no doubt remains popular because it can be used to remotely steal millions of dollars. Last year, for example, security researchers said that the Eurograbber gang, which was using a version of Zeus, had stolen an estimated $47 million from more than 30,000 corporate and private banking customers. The alleged ringleaders of that operation -- which included an estimated 20 people -- were arrested in April.

When it comes to online crime, gangs are drawn to financial malware toolkits -- not just Zeus -- because even a small number of people, who may not have advanced computer skills, can steal money relatively easily. Britain's Metropolitan Police Service this week arrested four people on charges that they'd used banking malware. Gediminas Simkus, 31, and Volodymyr Kurach, 31, were arrested on suspicion of stealing £1 million (US$1.64 million) from two British banks. Two women, aged 24 and 27 but not named in news reports, were also arrested and are out on bail, while the men are in jail pending a Thursday court hearing.

Police declined to discuss the malware that was allegedly employed by the two men. "For operational reasons, I'm afraid we are not willing to divulge the specific type of malware used at this time," a Metropolitan Police spokesman said via email.

But the script for these banking malware attacks remains the same, regardless of which crimeware toolkit gets used. "These arrests by the Met's Cyber Crime Unit follow an investigation into what we suspect is an international and organized crime targeting a number of bank customers in London and across the UK," Jason Tunn, a trainee detective chief inspector with the cybercrime unit, told UK crime news website Crime & Justice. "The victims have been hoodwinked by malware-carrying emails purporting to be from their banks, and subsequently had money taken from their accounts."

Mathew Schwartz is a freelance writer, editor, and photographer, as well the InformationWeek information security reporter.

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