Mastering ICS/OT Security: Blue, Red, and Purple Team Strategies

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Introduction

Industrial Control Systems (ICS) and Operational Technology (OT) security require a specialized approach beyond traditional IT security. With unique risks and protocols, teams must collaborate to defend critical infrastructure. This article breaks down the roles of Blue, Red, and Purple Teams in ICS/OT security and provides actionable techniques for each.

Learning Objectives

  • Understand the distinct roles of Blue, Red, and Purple Teams in ICS/OT security.
  • Learn key tools and commands used by each team for monitoring, attacking, and improving defenses.
  • Apply hands-on techniques to strengthen ICS/OT security postures.

You Should Know

1. Blue Team: Defending ICS/OT Systems

Objective: Detect and respond to threats without disrupting operations.

Key Tools & Commands:

  • Zeek (Bro) for OT Traffic Analysis 
    zeek -i eth0 -C local.zeek

    What it does: Monitors network traffic for anomalies in ICS protocols like Modbus/TCP.
    How to use: Run this command on a sensor node to log and analyze OT traffic.

  • Suricata with ICS Rulesets 

    suricata -c /etc/suricata/suricata.yaml -i eth0

    What it does: Detects malicious activity in industrial networks using custom ICS signatures.
    How to use: Deploy on an OT network tap and fine-tune rules for your environment.

  • Grafana for OT Dashboards 

    docker run -d -p 3000:3000 grafana/grafana

    What it does: Visualizes OT security events from SIEM logs.
    How to use: Integrate with tools like Elasticsearch to monitor real-time ICS alerts.

2. Red Team: Simulating ICS Attacks

Objective: Test defenses by emulating real-world ICS threats.

Key Tools & Commands:

  • Nmap for ICS Reconnaissance 
    nmap -sV --script modbus-discover.nse 192.168.1.100

What it does: Identifies Modbus devices and vulnerabilities.

How to use: Run in a controlled environment to map OT assets.

  • PLC Exploitation with Metasploit 
    msfconsole -q -x "use exploit/plc/siemens_s7_300; set RHOST 192.168.1.50; exploit"

    What it does: Simulates attacks on Siemens S7 PLCs.
    How to use: Only execute in authorized penetration tests.

  • Coil Replay Attacks with PCAP Tools 

    tcpreplay -i eth0 attack_traffic.pcap

    What it does: Replays captured OT traffic to test detection.
    How to use: Use in Purple Team exercises to validate defenses.

3. Purple Team: Bridging Detection and Attack Simulation

Objective: Improve security by aligning Red and Blue Team findings.

Key Techniques:

  • MITRE ATT&CK for ICS Mapping 
    python3 mitre_ics_mapper.py --tactic TA0043

    What it does: Maps adversary tactics to ICS-specific defenses.
    How to use: Run post-exercise to refine detection rules.

  • SIEM Rule Tuning with Sigma 

    title: Suspicious S7 Commands 
detection: 
selection: 
protocol: "S7comm" 
command: "0x32" 
condition: selection

    What it does: Creates custom SIEM rules for ICS threats.
    How to use: Deploy in Splunk/Elasticsearch for real-time alerts.

4. Hardening ICS Networks

Objective: Reduce attack surfaces in OT environments.

Key Commands:

  • Disabling Unused Industrial Protocols 
    sudo systemctl disable modbus-tcp.service

What it does: Reduces exposure to protocol-based attacks.

  • Segmenting OT Networks with Firewalls 
    iptables -A FORWARD -p tcp --dport 502 -j DROP

What it does: Blocks unauthorized Modbus traffic.

5. Training and Continuous Improvement

Objective: Build team expertise through hands-on labs.

Key Resources:

  • Labshock for ICS/OT Training 
    git clone https://github.com/labshock/ics-drills.git

What it does: Provides realistic ICS attack/defense scenarios.

What Undercode Say

  • Key Takeaway 1: ICS security requires specialized tools and collaboration between teams.
  • Key Takeaway 2: Continuous Purple Team exercises are critical for refining defenses.

Analysis: Unlike IT security, ICS/OT environments prioritize availability over confidentiality. Teams must balance security with operational continuity. Tools like Zeek, Suricata, and MITRE ATT&CK for ICS help bridge gaps, but real-world training (e.g., Labshock) is essential for preparedness.

Prediction

As ICS/OT attacks rise (e.g., ransomware targeting SCADA), organizations will invest more in cross-functional security teams. Automation and AI-driven anomaly detection will become standard, but human expertise in OT protocols will remain irreplaceable.

Final Thought: Start integrating Blue, Red, and Purple Team strategies today—before an attacker forces your hand.

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