In OT PLC risk, which action is most risky if an attacker gains access?

• A. Modifying register values in a PLC
• B. Reading operation logs
• C. Adding sensors
• D. Rebooting devices remotely

Answer: (A)

In OT PLC risk scenarios, the strongest danger comes from directly altering the values that drive the process. A PLC’s registers hold the real-time control data: setpoints, control outputs, mode flags, and safety interlocks. If an attacker tinkers with these values, the plant can suddenly behave in unsafe or damaging ways—overheating, overpressurization, incorrect valve positions, or unsafe startup/shutdown sequences. This kind of manipulation bypasses normal safety checks and can lead to physical harm, equipment damage, or widespread process instability.

Reading operation logs is largely passive and doesn’t change how the system operates, so it mainly risks information disclosure if sensitive data is exposed. Adding sensors might complicate data integrity or enable spoofing of readings, but it doesn’t immediately override the plant’s control decisions. Rebooting devices remotely can cause outages or downtime and may disrupt operations, but it’s typically mitigated by watchdogs, redundancies, and recovery procedures, making it less immediately dangerous than altering core control values.