A cybercrime group has maintained a Trojan horse for nearly three years has stolen the log-ons to more than 300,000 online bank accounts and almost as many credit cards, according to researchers at RSA Security 's FraudAction Research Labs.
The RSA team has tracked the Sinowal Trojan, also known as Mebroot and Torpig, to a drop server that contained the stolen credentials, said Sean Brady, the product marketing manager for RSA's ID and access assurance group.
"The sheer enormity of this makes this unique," said Brady. "And the scale is very unusual." All told, the gang behind Sinowal managed to obtain access to nearly half a million bank accounts and credit cards, a volume RSA dubbed "ruthless" and "extraordinary."
"And the fact that the Trojan was managed by one group through its history, and maintained for nearly three years is also very unusual," Brady said.
RSA uncovered records that showed the Trojan had been in active operation since at least February 2006. "In malware life cycles, that's ancient, and to keep it up required a high degree of resources and effort."
The company's researchers first got onto Sinowal's trail after they captured a sample of the Trojan. An analysis of its code laid out a map back to the drop server. That server was another unusual characteristic of the malware.
"Infection points and drop points go up and down all the time," Brady said. "They typically have very short life spans. But this drop site not only stayed up, it showed a sustained collection of log-ons."
Brady also credited Sinowal's longevity to its authors' skills and secrecy.
The Trojan has been revised more or less constantly and the group is also more secretive than most. "They don't outsource," said Brady, "and [they] have all the necessary expertise in-house. They don't open their toolkits to other hackers, either. We suspect that the closed-loop nature of the group contributed to their ability to remain undetected."
Sinowal has infected hundreds of thousands of PCs worldwide during its run, and continues to attack machines. Once on a system, it waits for the user to enter the address to an online bank, credit card company site or other 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 to other Trojans.
"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 anti-virus software. "They struggle to find this one," Brady said.
That's not surprising: the Trojan 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 Trojan is nearly invisible to security software. Security vendors have complained for months about how tough the malware is to spot.
RSA 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 Russia was the one region that had no infections."
Cyber crooks will often forgo infecting machines in their own country in the hope that local law enforcement will not come calling, or if they do find out about the attacks, will put any action low on their priority list.
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