In what could be a sign of things to come in ATM fraud, a highly sophisticated and well-funded criminal gang targeted an overseas bank and commandeered at least four of its ATMs with malware-rigged USB sticks in order to empty them of cash.

Tillmann Werner, a researcher for CrowdStrike, said the organized crime group cracked open the ATMs and plugged in the USB stick containing a DLL exploit payload. The payload reconfigured the ATM system such that the attackers controlled 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 said.

"They crack the ATM open and plug in the USB drive. It's risky, but nevertheless, it works," Werner said.

Werner declined to name the victim bank nor the brand of ATM it runs. The attacks still appear to be underway, he said. "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.

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