What is Network Monitoring?
Network monitoring is the process by which network traffic, devices and performance are continuously observed in order to quickly detect and resolve faults, anomalies or cyber threats.
In OT environments, network monitoring is crucial for business continuity, safety and visibility of industrial communication between PLCs, SCADA, HMIs and field devices.
🧠 How does network monitoring work?
- Data collection via:
- SNMP (status and performance data)
- Syslog (log messages)
- SPAN ports or TAPs (traffic analysis)
- ICMP or active ping checks
- Analysis of status, traffic and behaviour via tools or dashboards
- Alerts on anomalies, outages or policy violations
- Logging and trending for historical insight and forensic investigation
Monitoring tools often use dashboards, graphs and threshold values to provide real-time visibility.
🏭 Application of network monitoring in OT networks
- Detection of failed PLCs, Drives or Switches
- Visualisation of network performance and communication paths
- Real-time alerts on suspicious traffic or ARP spoofing
- Historical analysis of Modbus TCP traffic during faults
- Integration with SIEM platforms for security monitoring
- Monitoring of remote connections via VPN or Remote Access
Network monitoring helps with troubleshooting, preventive maintenance and cyber resilience.
🔍 Network monitoring vs. network security
| Aspect | Network monitoring | Network security |
|---|---|---|
| Purpose | Visibility, availability and performance | Protection against threats |
| Technologies | SNMP, Syslog, SPAN, ICMP, dashboards | Firewall, IDS, Zero Trust, ACL |
| Reactive/proactive | Proactive (trends and status) + reactive (alerts) | Mostly preventive or blocking |
| Use in OT | Yes – crucial for uptime | Yes – essential for segmentation and control |
🔐 Security considerations
- Monitoring data may be sensitive – secure communication with TLS and SNMPv3
- Use a separate VLAN or network segment for monitoring traffic
- Restrict access to monitoring tools via RBAC and Firewall
- Connect monitoring to SIEM for centralised correlation and logging
- Include access to monitoring portals in the Audit or compliance policy
Combine network monitoring with detection and logging for full OT visibility.
📌 In summary
Network monitoring provides visibility into the performance, availability and anomalies of industrial networks. It forms the foundation of fast incident response, process continuity and cyber hygiene in modern OT environments.