Hackers planted a Raspberry Pi equipped with a 4G modem in the network of an unnamed bank in an attempt to siphon money out of the financial institution’s ATM system, researchers reported Wednesday.
The researchers with security firm Group-IB said the “unprecedented tactic allowed the attackers to bypass perimeter defenses entirely.” The hackers combined the physical intrusion with remote access malware that used another novel technique to conceal itself, even from sophisticated forensic tools. The technique, known as a Linux bind mount, is used in IT administration but had never been seen used by threat actors. The trick allowed the malware to operate similarly to a rootkit, which uses advanced techniques to hide itself from the operating system it runs on.
End goal: Backdooring the ATM switching network
The Raspberry Pi was connected to the same network switch used by the bank’s ATM system, a position that effectively put it inside the bank’s internal network. The goal was to compromise the ATM switching server and use that control to manipulate the bank’s hardware security module, a tamper-resistant physical device used to store secrets such as credentials and digital signatures and run encryption and decryption functions.
