Fast Flux Botnet Nets Fraudsters $78 Million

What does it take to build a cutting-edge, highly automated series of attacks against banking systems, powered by financial malware and bulletproof hosting services? For starters, it helps to have extensive experience using the Zeus and SpyEye financial malware toolkits.

That's just one finding from "Operation High Roller Revisited," a new report released this week by McAfee and Guardian Analytics, which provides greater insights into the gangs that appear to be behind a massive number of attacks launched against financial institutions from servers located in Russia, Albania and China.

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The criminals have stolen an estimated $78 million, in part by using financial malware. "These campaigns, like many other attempts at fraud, originated in Eastern Europe, so it is not surprising that the actors had an extensive history of Zeus and SpyEye activity," read the report, which was written by Ryan Sherstobitoff, a threat researcher at McAfee.

But the attackers' sophistication has also continued to increase. "Prior to conceiving Operation High Roller, our data shows that the fraudsters actively participated in early automated transfer systems against consumers and some business accounts and actively used Zeus and SpyEye in these attacks," said Sherstobitoff in a blog post. "These initial efforts were likely their test ground to gain knowledge of financial systems and their various fraud prevention practices." From there, he said, the gangs progressed to more advanced attacks, including launching highly automated transfer system exploits against European banks at the end of 2011. Earlier this year, the attacks were expanded to exploit banks in North America as well.

The new report updates research released in June by McAfee and Guardian Analytics, which first detailed Operation High Roller. A total of 12 different criminal gangs appear to be involved in the attacks, which have been launched against financial institutions of every size, from credit unions to large banks. Most of the attacks documented in that report used Zeus and SpyEye malware to attempt to transfer money out of accounts located in the United States and the Netherlands.

The groups behind Operation High Roller have tended to focus only on certain industries. "Typically these campaigns have no precise target other than high net worth businesses with significant cash flow," according to the report. Interestingly, however, the U.S. attacks seemed to focus on commercial banking involving businesses in the manufacturer and import/export industries, as well as state and local governments.

Their attacks mix manual exploits with quite sophisticated automated attacks, which were launched against thousands of financial institutions in Europe and North America. To help avoid detection, criminals launched their automated attacks not from compromised PCs that were part of a botnet but from servers. These servers appeared to be leased from so-called bulletproof hosting providers, predominantly located in Russia, China, or other parts of Asia, which offer quite lenient "acceptable use" policies and terms of service for their systems.

Now the researchers have found that the criminals involved in Operation High Roller had previously used elements of the same infrastructure to launch a series of prior attacks that involved automated transfer system attack tools, which are designed to automatically drain targeted bank accounts.

In the past, malware such as Zeus might use Web injection files to modify target websites, then attempt to trick users into inputting their credentials, at which point attackers could manually steal their money by transferring it into another account. Automated transfer systems, however, take users out of the equation because they "allow cybercriminals to automatically transfer funds from victims' accounts to their own ones without leaving traces of their presence," according to Trend Micro threat researcher Loucif Kharouni. "Instead of merely passively stealing information, [they] allow cybercriminals to instantly carry out financial transactions that could deplete users' bank accounts without their knowledge."

McAfee's Sherstobitoff said that researchers had traced some of the attacks to a server located in Kemerovo, Russia. But that server pointed to other servers, some located in China and one in San Jose, Calif. "These connections were the first indication that this was a 'fast-flux' botnet with many levels of complication," he said. "The fast-flux technique allows malware to hide itself in an array of compromised servers and increase its lifespan."

Going forward, expect the gangs involved in Operation High Roller to continue pushing the malicious-banking-attack state of the art. "Financial institutions, regulators, and security researchers should expect the likely next target to be Automated Clearing House payment channels," said Sherstobitoff. "The fraudsters will build on the methods, malware, and infrastructure employed in Operation High Roller, laced with new ideas and locations to be discovered. We should be looking for any signs of 'test cases' against these systems and tracking interactions to uncover malicious sites and infrastructure."

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