Getting Started in ICS/OT Cybersecurity: A Free 25-Hour Course Guide

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Introduction

Industrial Control Systems (ICS) and Operational Technology (OT) cybersecurity are critical fields as industries increasingly digitize their infrastructure. Mike Holcomb’s free 25-hour YouTube course provides foundational knowledge, covering ICS/OT security principles, network architecture, threat management, and penetration testing. With over 70,000 views and 1,000+ live participants, this course is a valuable resource for IT professionals transitioning into OT security.

Learning Objectives

  • Understand core ICS/OT cybersecurity concepts and challenges.
  • Learn secure network architecture and asset management for industrial environments.
  • Gain insights into threat detection, incident response, and penetration testing in ICS/OT.

You Should Know

1. ICS/OT Network Segmentation Best Practices

Command (Cisco IOS):

enable 
configure terminal 
interface GigabitEthernet0/1 
switchport mode access 
switchport access vlan 10 
exit

What This Does: Isolates OT devices in a separate VLAN to prevent lateral movement from IT networks.

Step-by-Step Guide:

1. Access the switch’s CLI.

2. Enter global configuration mode (`configure terminal`).

  1. Select the interface connected to the OT device (interface GigabitEthernet0/1).
  2. Set the port to access mode (switchport mode access).
  3. Assign the port to a dedicated OT VLAN (switchport access vlan 10).

2. Detecting Unauthorized Modbus Traffic

Command (Wireshark Filter):

tcp.port == 502 && modbus

What This Does: Filters network traffic to detect Modbus/TCP communications on port 502, commonly used in ICS environments.

Step-by-Step Guide:

1. Open Wireshark and start capturing traffic.

  1. Apply the filter tcp.port == 502 && modbus.
  2. Analyze packets for unauthorized or suspicious Modbus requests.

3. Hardening Windows ICS Workstations

Command (PowerShell):

Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Control\Lsa" -Name "RestrictAnonymous" -Value 1

What This Does: Disables anonymous enumeration of system shares and accounts, reducing attack surface.

Step-by-Step Guide:

1. Open PowerShell as Administrator.

  1. Run the command to modify the registry key.
  2. Reboot the system for changes to take effect.

4. ICS Asset Discovery with Nmap

Command (Linux):

nmap -sS -p 1-1024 --script modbus-discover <OT_IP_Range>

What This Does: Scans for open Modbus ports and identifies ICS devices.

Step-by-Step Guide:

1. Install Nmap (`sudo apt install nmap`).

  1. Run the scan against the OT network range.

3. Review results for exposed ICS services.

5. Securing ICS Protocols with Firewall Rules

Command (Linux iptables):

iptables -A INPUT -p tcp --dport 502 -j DROP

What This Does: Blocks external access to Modbus/TCP (port 502) unless explicitly allowed.

Step-by-Step Guide:

1. Access the Linux firewall.

  1. Add the rule to drop incoming Modbus traffic.

3. Save rules (`iptables-save`).

What Undercode Say

  • Key Takeaway 1: ICS/OT security requires a different approach than IT security due to legacy systems and real-time operational constraints.
  • Key Takeaway 2: Network segmentation, protocol filtering, and asset visibility are foundational to securing industrial environments.

Analysis:

The increasing convergence of IT and OT networks exposes critical infrastructure to cyber threats. Holcomb’s course bridges the knowledge gap for IT professionals entering OT security. Hands-on techniques like VLAN segmentation, protocol filtering, and asset discovery are essential for defending ICS environments. As ransomware attacks on industrial systems rise, structured training like this is crucial for building a skilled workforce.

Prediction

With growing digitization in manufacturing, energy, and utilities, ICS/OT cybersecurity will become a top priority. Professionals with OT security expertise will be in high demand, and free resources like Holcomb’s course will play a key role in workforce development. Expect stricter regulations and increased adoption of zero-trust frameworks in industrial networks.

🔗 Resources:

https://youtube.com/@utilsec
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