Crucial Exams

Certified Ethical Hacker (CEH) Practice Question

During a security assessment of a municipal water-treatment facility you prove that, once an attacker gains Layer 2 access to the control LAN, they can push malicious ladder-logic to the plant's programmable logic controllers (PLCs) and alter the chemical dosing process. The site already uses firewalls, strong authentication on engineering workstations, and segmented VLANs, but management remains concerned about logic tampering by a rogue insider or a compromised HMI. Which additional OT-specific countermeasure would most effectively block unauthorized logic downloads to the PLCs even if the network defenses are bypassed?

  • Deploy a network IDS that triggers alerts on Modbus function codes 5, 6, and 16.

  • Place the PLCs behind an additional stateful inspection firewall on the control LAN.

  • Enforce time-based one-time password (TOTP) authentication for all SCADA HMI logins.

  • Lock each PLC's hardware mode switch in the RUN position to disable programming writes.

Certified Ethical Hacker (CEH)
Mobile Platform, IoT, and OT Hacking
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