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'Ruthless' Trojan horse steals 500k bank, credit card log-ons

October 31, 2008 12:00 PM ET

Sinowal has infected hundreds of thousands of PCs worldwide during its run, and it continues to attack machines. Once on a system, the malware waits for the user to enter the address to an online bank, credit card company site or another financial URL, then substitutes a fake in place of the real thing. It's triggered by more than 2,700 specific Web addresses, a massive number compared with other Trojan horses.

The fake sites collect log-on usernames and passwords to banks and other financial institutions and dupe users into disclosing information those organizations never collect online, such as Social Security numbers. The Trojan then transmits the stolen credentials and data to the drop server.

"This is one of the more sophisticated pieces of malware out there," said Brady.

One reason Sinowal has been so successful is that it's rarely detected by antivirus software. "They struggle to find this one," Brady said. That's not surprising. The Trojan horse includes rootkit elements that infect the PC's master boot record (MBR), the first sector of a hard drive. Because the hardware looks to that sector before loading anything else, Windows included, the Sinowal is nearly invisible to security software. Security vendors have complained for months about how tough the malware is to spot.

RSA Security suspects that the group responsible for Sinowal is based in Russia. "The distribution was truly global, but the one statistical anomaly that we noticed was [that] Russia was the one region that had no infections." Cybercrooks will often forgo infecting machines in their own country in the hope that local law enforcement authorities will not come calling or that if they do find out about the attacks, they'll put any action low on their priority list.

"This is the biggest find we've made to date," confirmed Brady. "But one reason why we're talking is so we can connect to [the affected] financial institutions." RSA has notified authorities and the banks and credit card companies with which it has existing relationships, but it needs help in contacting others, he said.

Read more about Security in Computerworld's Security Topic Center.

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