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OT Cybersecurity

Security Monitoring

Detection of anomalies and intrusions on OT networks.

CybersecurityOT Network

Overview

Security monitoring for OT observes the network's habits — and OT habits are so regular that novelty itself is a high-quality signal.

Engineering purpose

Detect intrusions and anomalies early, from passive observation that cannot disturb fragile industrial devices.

How it works

SPAN/TAP mirrors feed passive analyzers that parse industrial protocols; baselines of devices, connections, and function codes define normal; new device, new flow, or new command type raises events tied to response runbooks.

  • Passive monitoring via SPAN/TAP observes industrial protocols without touching fragile devices.
  • OT traffic is highly regular — new device, new connection, or new function code is a strong signal.
  • Detection without a response plan is noise: every alert class needs a defined owner and action.

Common faults

Monitoring only the IT boundary while intra-OT traffic goes unseen; alert classes without owners decaying into noise; baselines never updated after legitimate plant changes; active scanning crashing sensitive devices.

Diagnostic checks

  1. 1Verify monitoring sees traffic from every zone, not just the IT boundary.
  2. 2Review recent new-device and new-connection alerts against the asset inventory.
  3. 3Verify sensor coverage actually includes every zone's traffic, not merely the convenient core switch.

Safety notes

Use passive collection in OT — active scanning has bricked PLCs and instruments; anything active needs explicit engineering approval and a maintenance window.

Commissioning notes

Establish the traffic baseline during known-normal operation, assign an owner and action to every alert class, and rehearse the response path.

Related concepts

Passive SPAN/TAP collection, behavioral baselining, industrial protocol parsing, alert ownership, anomaly types.

monitoring · ids · intrusion · detection · anomaly · unknown device · پایش امنیتی · تشخیص نفوذ · ناهنجاری · ناشناس

Related engineering cases

Related articles

Network Segmentation

Zones, conduits, and DMZ design per IEC 62443.

Access Control

Identity, remote access, and least privilege in OT.

Audit & Logging

Audit trails, log collection, and compliance evidence in OT.

Industrial Protocols

Fieldbus and industrial Ethernet selection and diagnostics.

When Hermes Brain uses this article

Cited for unknown devices on OT networks, intrusion detection design, anomaly triage, and monitoring coverage questions.

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