Deploying Intrusion Detection Systems (IDS) in Operational Technology (OT) environments is challenging. Unlike IT networks, OT networks require specialized handling to avoid disruptions. Here’s why many OT IDS deployments fail and how to optimize them.
Best Practices for OT IDS Deployment
✅ Use Passive Monitoring – Avoid inline deployments that can disrupt critical operations. Tools like Zeek (Bro IDS) or Suricata in passive mode are ideal.
✅ Understand OT Protocols – Use IDS rules tailored for Modbus, DNP3, IEC 60870-5-104, and other industrial protocols.
✅ Capture Normal Traffic Patterns – Baseline legitimate traffic to reduce false positives. Tools like Wireshark or Tshark help analyze OT traffic.
✅ Test in a Lab First – Simulate attacks in a controlled environment before live deployment.
Common Mistakes to Avoid
❌ Applying Generic IT Rules – IT-focused IDS rules (e.g., Snort) often fail in OT. Use OT-specific rulesets.
❌ Ignoring OT Team Input – OT engineers understand system behavior best. Collaborate with them.
❌ Overloading Network Devices – Many OT switches can’t handle SPAN port traffic. Use network taps instead.
❌ Leaving IDS Unmanaged – Continuously tune rules to reduce false positives.
You Should Know: Essential OT Security Commands & Tools
1. Passive Traffic Analysis
Capture OT traffic with tcpdump tcpdump -i eth0 -w ot_traffic.pcap Analyze with Wireshark (GUI) wireshark ot_traffic.pcap Filter Modbus traffic in Wireshark modbus Use Zeek (Bro) for OT traffic logging zeek -i eth0 -C
2. Simulating OT Attacks in a Lab
Use Python to craft Modbus packets
from pymodbus.client import ModbusTcpClient
client = ModbusTcpClient('192.168.1.10')
client.write_register(0, 1000) Simulate malicious write
Test IDS detection with SCADA-specific attacks
msfconsole
use auxiliary/scanner/scada/modbusdetect
set RHOSTS 192.168.1.0/24
run
3. OT-Specific IDS Rules (Suricata Example)
Detect unauthorized Modbus function codes alert modbus any any -> any any (msg:"Unauthorized Modbus Function Code"; modbus_func:6; sid:1000001;) Detect DNP3 recon commands alert dnp3 any any -> any any (msg:"DNP3 Recon Attempt"; dnp3_func:0x14; sid:1000002;)
4. Network Monitoring & Tuning
Check switch SPAN port load (Cisco) show monitor session 1 Use tcpreplay to test IDS before deployment tcpreplay -i eth0 ot_traffic.pcap Verify IDS logs for false positives grep "false_positive" /var/log/suricata/fast.log
What Undercode Say
OT IDS deployments require a balance between security and operational stability. Unlike IT, OT networks prioritize safety over strict access control. Key takeaways:
– Passive monitoring is king – Avoid inline deployments.
– OT protocols need specialized rules – Generic IT rules fail.
– Test before deployment – Use lab environments to simulate attacks.
– Continuous tuning is mandatory – OT networks evolve; IDS rules must adapt.
Expected Output:
A well-tuned OT IDS should:
✔ Detect malicious OT protocol manipulation.
✔ Minimize false positives through baselining.
✔ Integrate with OT team workflows.
✔ Avoid disrupting critical industrial processes.
Prediction:
As OT-IT convergence grows, machine learning-based anomaly detection will become crucial. However, lack of public OT attack datasets remains a hurdle. Future OT IDS solutions will likely combine protocol-aware rules with AI-driven behavioral analysis.
( extracted from Zakhar Bernhardt’s LinkedIn post on OT IDS failures.)
References:
Reported By: Zakharb Most – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
