Individual skill
monitoring-scada-modbus-traffic-anomalies
Monitors Modbus TCP traffic on SCADA and ICS networks to detect anomalous function code usage, unauthorized register writes, and suspicious communication patterns. The analyst uses deep packet inspection with pymodbus, Scapy, and Zeek to baseline normal PLC/RTU communication behavior, then applies statistical and rule-based anomaly detection to identify reconnaissance, parameter manipulation, and denial-of-service attacks targeting Modbus devices on port 502. Activates for requests involving Modbus traffic analysis, SCADA network monitoring, ICS anomaly detection, PLC security monitoring, or OT network threat detection.
internal/tools/skills/data/ot-ics-security/monitoring-scada-modbus-traffic-anomalies/SKILL.md
Source commit d42f381ad34843e71a42658e5c57290c713e85af
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- Observed behavior
- Instructions only
- Last checked
- Nov 9, 2026
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Repository context
- Repository stars (not skill ratings)
- 1,315
- Repository last updated
- Nov 8, 2026
- License
- Apache-2.0
Observed agent integration: No specific integration evidence. Standard SKILL.md installation does not imply verified compatibility.
- cybersecurity Repository topic
- security Repository topic
- bug-bounty Repository topic
- automation Repository topic
- autonomous-pentesting Repository topic
- ai-agent Repository topic
- ai-security Repository topic
- ethical-hacking Repository topic
- golang Repository topic
- penetration-testing Repository topic
- modbus-tcp Declared skill tag
- scada Declared skill tag
- ics-security Declared skill tag
- deep-packet-inspection Declared skill tag
- anomaly-detection Declared skill tag
- ot-monitoring Declared skill tag
- security Derived category
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Read excerpt
# Monitoring SCADA Modbus Traffic Anomalies
## When to Use
- Monitoring OT/ICS networks for unauthorized Modbus commands targeting PLCs, RTUs, or HMIs
- Detecting reconnaissance activity such as Modbus device enumeration (function code 43, Read Device Identification)
- Identifying unauthorized write operations (function codes 05, 06, 15, 16) to coils and holding registers that could alter physical process parameters
- Baselining normal Modbus communication patterns and alerting on deviations in function code distribution, register access ranges, or timing intervals
- Investigating suspected sabotage or insider threats manipulating SCADA process values through Modbus register writes
**Do not use** on networks without authorization from the asset owner, for active injection or fuzzing against production SCADA systems, or as a replacement for safety-instrumented systems (SIS) that provide physical process protection.
## Detection Gaps & Validation
Modbus monitoring misses attacks when it watches the wrong layer. Close these gaps: