How does OT network security monitoring work?
OT network security monitoring works by passively observing all traffic on an industrial network without sending any packets or interacting with devices. A monitoring appliance connects to a network TAP or mirror port and analyzes every connection using protocol-specific parsers for Modbus, DNP3, EtherNet/IP, and standard TCP/IP. When the observed traffic matches a detection rule, an alert is generated. This approach provides visibility into unauthorized access, configuration changes, and anomalous behavior without any risk to the industrial process.
What is passive network monitoring?
Passive network monitoring means observing network traffic without generating any traffic of your own. The monitoring device has no IP address on the monitored network and is physically incapable of sending packets into it. This is critical in OT environments where even a single unexpected packet could disrupt a PLC or safety system. Passive monitoring provides complete visibility with zero risk to operations.
How do I detect unauthorized Modbus writes?
Unauthorized Modbus writes are detected by monitoring Modbus TCP traffic on port 502 for write function codes (5, 6, 15, 16, 22, 23) and comparing the source IP against a baseline of authorized devices. During an initial learning period, the monitoring system records which devices normally issue write commands. After the baseline is established, any write command from a new or unauthorized source triggers an immediate alert. This catches both external attackers and misconfigured internal systems.
What is NERC CIP compliance monitoring?
NERC CIP compliance monitoring automates the collection of evidence required by the North American Electric Reliability Corporation Critical Infrastructure Protection standards. This includes continuous monitoring logs (CIP-007), electronic security perimeter access records (CIP-005), and configuration change documentation (CIP-010). Automated monitoring generates audit-ready evidence packages that can be handed directly to a NERC auditor without manual preparation. Non-compliance penalties can reach $1 million per day per violation.
Do I need to install software on my PLCs?
No. Passive OT monitoring requires zero software installation on any industrial device. The monitoring appliance connects to your network infrastructure, not to individual PLCs, RTUs, or HMIs. This means there is no risk of disrupting device firmware, no compatibility testing required, and no maintenance window needed for deployment. The appliance is physically separate from your control systems.
Can OT security monitoring work without internet?
Yes. A properly designed OT monitoring appliance continues to detect threats and store alerts locally even when internet connectivity is completely unavailable. The detection rules run on the appliance itself, not in the cloud. Log data and alerts queue on the device and are automatically uploaded when connectivity is restored. This is essential because many OT environments have intermittent or restricted internet access.
What is the difference between IT and OT security?
IT security focuses on protecting data confidentiality, integrity, and availability on computer systems and networks. OT security focuses on protecting physical processes controlled by industrial systems. The key difference is consequence: an IT breach typically results in data loss, while an OT breach can cause physical damage, environmental harm, or safety incidents. OT security must also account for legacy devices that cannot be patched, protocols without authentication, and the absolute priority of operational availability over all other concerns.