Tillmann Werner, a researcher for CrowdStrike, says the organized crime group cracked open the ATM machines and plugged in the USB stick containing a DLL exploit payload. The payload reconfigured the ATM system such that the attackers control it and allowed money mules to steal all of the cash stored in those machines. There has been a single arrest so far -- a money mule -- and the attacks may possibly have incurred millions of dollars in losses. These attacks are expected against other banks as well, he says.
"They crack the ATM open and plug in the USB drive. It's risky, but nevertheless, it works," Werner says.
Werner declined to name the victim bank or the brand of ATM machines it runs. The attacks still appear to be under way, he says. "The fact that such a sophisticated group is operating right now is the most important fact. Another thing that's interesting is banks in Germany potentially have the same issue, although we haven't seen an attack like that in Germany so far," Werner says.
The attackers physically took apart the ATM machines and inserted a USB stick with a malicious DLL installer into the printer port, giving them control of the ATM's Windows XP-based operating system. When a network connection is interrupted to the ATM, it automatically reboots, doing so from the malicious USB. The installer program collects information from the ATM system and also contains a log file for the attackers.
"It's a DLL injection file attack into the running process [of the ATM], and then you have code running in that process, and they can do what they want," Werner says.
One member of the gang in the heist was caught when he went to one of the ATMs to cash out. The cash-out works like this: An attacker types in a 12-digit code that then displays the malicious menu on the ATM screen. He answers a challenge question, and then calls one of his accomplices for a response code, which he inputs to dispense the cash from the ATM. The entire transaction of emptying the ATM takes a few short minutes.
Unlike the ATM Ploutus malware that was discovered last year that targeted bank customers during their ATM transactions, this attack goes after the bank's cash in the ATMs. "It's not related to Ploutus," he says, which is "child's play" compared with this new, more advanced method that steals from the bank itself.
"Attacks against ATMs mostly have been skimming attacks," he says. "With this attack, you can empty a whole ATM and make a lot of money ... It definitely takes a mafia-like organization to pull off such an attack."
The victim bank discovered the heist when its ATMs prematurely went empty of cash. "It doesn't leave any [other] traces," Werner says. The only clue is that the balance in the machine declines -- the theft transaction isn't detected.
There are ways to prevent such an attack, but with ATMs not built with software security in mind, it's tough to defend against it today. "You have to secure the PC, but that's easier said than done," Werner says. The best bet is to add a boot password to the system, which would prevent this attack, or to encrypt the ATM's hard drive.
The attack could work on banks in the U.S. as well, he says. The attackers have different versions of the malware for different banks, he says. "It has nothing to do with the banking system. They're going after the machine that spits out the money," he says. "Maybe they're not attacking U.S. ATMs because they use less cash in their ATMs."
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