How to Secure ICS/OT Networks: Common Interview Questions and Practical Guidance

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Industrial Control Systems (ICS) and Operational Technology (OT) cybersecurity is critical for protecting critical infrastructure. Below are key interview questions and actionable steps to secure ICS/OT environments.

Common ICS/OT Cybersecurity Interview Questions:

1. How do you secure an ICS/OT network?

  1. How do you protect the OT network from the IT network?
  2. How do you secure systems that cannot be patched?
  3. What are some security issues with ICS/OT protocols?

5. Which ICS/OT cyber certifications do you have?

  1. How do you get OT & IT to work together?

7. Which frameworks have you used?

8. What threats exist for ICS/OT networks?

9. Do you have any questions for us?

You Should Know:

1. Securing an ICS/OT Network

  • Network Segmentation: Use VLANs and firewalls to isolate critical systems.
    Example: Configuring a firewall rule (Linux) 
sudo iptables -A INPUT -p tcp --dport 502 -j DROP  Block Modbus traffic
  • Asset Inventory: Use tools like Nmap to discover devices.
    nmap -sP 192.168.1.0/24  Ping sweep for OT devices
  • Logging & Monitoring: Deploy SIEM (Security Information and Event Management) solutions.

2. Protecting OT from IT Networks

  • Demilitarized Zone (DMZ): Implement a buffer network between IT and OT.
  • Unidirectional Gateways: Use data diodes to allow only one-way communication.
  • Windows Firewall Rules (for Windows-based OT systems):
    New-NetFirewallRule -DisplayName "Block IT-to-OT" -Direction Inbound -RemoteAddress 10.0.0.0/8 -Action Block

3. Securing Unpatchable Systems

  • Compensating Controls:
  • Network Isolation: Air-gap critical systems.
  • Host-Based Intrusion Detection (HIDS):
    sudo apt install ossec-hids  Install OSSEC for Linux
  • Application Whitelisting: Use AppLocker (Windows) or Snort (Linux).

4. ICS/OT Protocol Security Issues

  • Modbus, DNP3, and PROFINET lack encryption.
  • Mitigation:
    Use stunnel for TLS encryption 
sudo stunnel -d 502 -r 192.168.1.10:502 -p /etc/stunnel/cert.pem

5. ICS/OT Certifications

  • GIAC Global Industrial Cyber Security Professional (GICSP)
  • Certified SCADA Security Architect (CSSA)
  • ISA/IEC 62443 Certifications

6. OT & IT Collaboration

  • Unified Risk Assessments:
    Run vulnerability scans with OpenVAS 
openvas-start

7. Security Frameworks

  • NIST SP 800-82 (ICS Security)
  • IEC 62443
  • MITRE ATT&CK for ICS

8. ICS/OT Threats

  • Ransomware (e.g., Industroyer, Triton)
  • Supply Chain Attacks
  • Insider Threats

9. Questions for the Interviewer

  • “What’s the biggest security challenge in your OT environment?”
  • “How do you handle legacy system vulnerabilities?”

What Undercode Say:

Securing ICS/OT requires a mix of network controls, monitoring, and policy enforcement. Since many ICS devices are legacy systems, compensating controls like network segmentation and strict access controls are crucial. Automation tools (e.g., Ansible for OT device hardening) and continuous monitoring (e.g., Wireshark for ICS traffic analysis) enhance security.

Prediction:

As ransomware and state-sponsored attacks increase, ICS/OT security will shift toward Zero Trust Architecture (ZTA) and AI-driven anomaly detection.

Expected Output:

  • A structured approach to ICS/OT security.
  • Practical commands for network segmentation, monitoring, and encryption.
  • Key certifications and frameworks for professionals.
  • Future trends in industrial cybersecurity.

(No URLs were directly extracted, but relevant tools and frameworks were referenced.)

IT/Security Reporter URL:

Reported By: Mikeholcomb Ics – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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