“Some of the uncommon parts of this case was the attacker’s use of bodily entry to put in a Raspberry Pi system,” Group-IB Senior Digital Forensics and Incident Response Specialist Nam Le Phuong wrote. “This system was related on to the identical community change because the ATM, successfully putting it contained in the financial institution’s inner community. The Raspberry Pi was geared up with a 4G modem, permitting distant entry over cellular information.”
To keep up persistence, UNC2891 additionally compromised a mail server as a result of it had fixed Web connectivity. The Raspberry Pi and the mail server backdoor would then talk by utilizing the financial institution’s monitoring server as an middleman. The monitoring server was chosen as a result of it had entry to nearly each server throughout the information middle.
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The Community Monitoring Server as an middleman between the Raspberry Pi and the Mail Server.
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Group-IB
As Group-IB was initially investigating the financial institution’s community, researchers observed some uncommon behaviors on the monitoring server, together with an outbound beaconing sign each 10 minutes and repeated connection makes an attempt to an unknown system. The researchers then used a forensic software to research the communications. The software recognized the endpoints as a Raspberry Pi and the mail server however was unable to establish the method names chargeable for the beaconing.
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Group-IB
The forensic triage software is unable to gather the related course of identify or ID related to the socket.
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Group-IB
The researchers then captured the system reminiscence because the beacons had been despatched. The evaluation recognized the method as lightdm, a course of related to an open supply LightDM show supervisor. The method gave the impression to be legit, however the researchers discovered it suspicious as a result of the LightDM binary was put in in an uncommon location. After additional investigation, the researchers found that the processes of the customized backdoor had been intentionally disguised in an try to throw researchers off the scent.
Phuong defined:
The backdoor course of is intentionally obfuscated by the menace actor by using course of masquerading. Particularly, the binary is known as “lightdm”, mimicking the legit LightDM show supervisor generally discovered on Linux methods. To boost the deception, the method is executed with command-line arguments resembling legit parameters – for instance,
lightdm –session little one 11 19 — in an effort to evade detection and mislead forensic analysts throughout post-compromise investigations.
These backdoors had been actively establishing connections to each the Raspberry Pi and the interior Mail Server.
As famous earlier, the processes had been disguised utilizing the Linux bind mount. Following that discovery, Group-IB added the approach to the MITRE ATT&CK framework as “T1564.013 – Conceal Artifacts: Bind Mounts.”
Group-IB didn’t say the place the compromised switching tools was situated or how attackers managed to plant the Raspberry Pi. The assault was detected and shut down earlier than UNC2891 was in a position to obtain its closing purpose of infecting the ATM switching community with the CakeTap backdoor.
