Which monitoring tools are appropriate for detecting unusual OT activity?

Which monitoring tools are appropriate for detecting unusual OT activity?

• A. Only antivirus on IT endpoints
• B. SIEM, IDS, and anomaly detection
• C. Manual review of logs once per year
• D. No monitoring in OT networks

Answer: (B)

Detecting unusual OT activity relies on layered monitoring that provides real-time visibility into OT networks and devices, plus the ability to recognize deviations from normal operations. SIEM, IDS, and anomaly detection work together to achieve this. SIEM collects and correlates logs from OT and IT sources, giving a centralized view and enabling alerts when events match suspicious patterns or show unusual sequences. IDS monitors network traffic and can detect known attack signatures or abnormal communication patterns across OT protocols like Modbus, DNP3, or IEC 60870-5. Anomaly detection builds a baseline of normal OT behavior—things like typical command frequencies, device interactions, and setpoint changes—and flags deviations that may indicate malware, misconfigurations, or unsafe changes. Using all three creates timely, actionable detections across the control network. For example, a sudden surge of write commands to a PLC, combined with unusual command sequences and an unexpected login, might trigger SIEM correlations and IDS alerts, while anomaly detection would flag behavior that falls outside the established OT baseline. This kind of coordinated visibility is essential in OT, where threats can impact safety and operations. Relying only on antivirus on IT endpoints misses OT-specific threats and protocols, as OT devices may not run standard antivirus or expose the same attack surfaces. Reviewing logs only once a year is far too slow to catch fast-moving threats or zero-days. And having no monitoring at all leaves OT networks blind to intrusions and anomalous behavior.

Detecting unusual OT activity relies on layered monitoring that provides real-time visibility into OT networks and devices, plus the ability to recognize deviations from normal operations. SIEM, IDS, and anomaly detection work together to achieve this.

SIEM collects and correlates logs from OT and IT sources, giving a centralized view and enabling alerts when events match suspicious patterns or show unusual sequences. IDS monitors network traffic and can detect known attack signatures or abnormal communication patterns across OT protocols like Modbus, DNP3, or IEC 60870-5. Anomaly detection builds a baseline of normal OT behavior—things like typical command frequencies, device interactions, and setpoint changes—and flags deviations that may indicate malware, misconfigurations, or unsafe changes. Using all three creates timely, actionable detections across the control network.

For example, a sudden surge of write commands to a PLC, combined with unusual command sequences and an unexpected login, might trigger SIEM correlations and IDS alerts, while anomaly detection would flag behavior that falls outside the established OT baseline. This kind of coordinated visibility is essential in OT, where threats can impact safety and operations.

Relying only on antivirus on IT endpoints misses OT-specific threats and protocols, as OT devices may not run standard antivirus or expose the same attack surfaces. Reviewing logs only once a year is far too slow to catch fast-moving threats or zero-days. And having no monitoring at all leaves OT networks blind to intrusions and anomalous behavior.