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Take All My Money: Penetrating ATMs

Fredrik Sandstom

Shares war stories, tooling, and operational hurdles from physical and logical penetration tests against automated teller machines (ATMs).

Summary

ATM Penetration Testing Realities

Automated Teller Machines (ATMs) combine physical security safes, specialized embedded hardware, and standard desktop operating systems. Penetration testing these machines requires navigating both logical software defenses and heavy physical security barriers.

Hardware Interception and Dispenser Attacks

Logical attacks against ATMs frequently exploit vulnerabilities in the communication bus between the core PC and the cash dispenser unit. Attackers connect hardware implants directly to internal USB or serial buses to issue unauthorized dispense commands, known as black-box attacks.

Operating System and Application Weaknesses

Legacy ATM operating systems often run unhardened Windows environments with weak application whitelisting and insecure maintenance accounts. Misconfigured kiosk modes and diagnostic utilities allow testers to break out to administrative command prompts.

Defensive Mitigations for Financial Terminals

Securing ATM fleets requires implementing end-to-end cryptographic communication between dispenser controllers and core software, enforcing strict full-disk encryption, and supervising physical enclosure tamper sensors.

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