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Introduction:
Operational Technology (OT) and Industrial Control Systems (ICS) form the backbone of critical infrastructure—power grids, water treatment plants, and manufacturing lines—yet cybersecurity training for these environments remains scarce and often expensive. A recent LinkedIn post by Mike Holcomb, a recognized OT/ICS security expert, curates seven free, high-quality courses from CISA and community sources, covering everything from foundational concepts to penetration testing and OSINT. This article extracts those resources, adds practical Linux/Windows commands, and delivers a step‑by‑step guide to mastering OT/ICS security without breaking the bank.
Learning Objectives:
- Identify and access the top free OT/ICS cybersecurity training courses, including CISA’s 100/200/300 levels and ISA/IEC 62443‑aligned content.
- Apply hands‑on techniques such as network scanning, Modbus traffic analysis, and vulnerability assessment using common Linux and Windows tools.
- Implement basic penetration testing and OSINT gathering specifically tailored to ICS/OT environments while understanding mitigation strategies.
You Should Know:
- CISA’s Foundational & Advanced ICS Courses (100/200/300 Level)
The Cybersecurity and Infrastructure Security Agency (CISA) offers free, self‑paced courses. The 100/200 level introduces ICS architecture, threats, and defense‑in‑depth. The ICS300 course dives into advanced topics like incident response and risk assessment.
Step‑by‑step guide to start and practice:
- Register for free at the CISA training portal using the links:
https://lnkd.in/espC8nri (100/200)
https://lnkd.in/esHkF4Ce (ICS300) - After completing the theory, simulate an ICS network to reinforce learning. On Linux, use `nmap` to scan for common OT protocols:
sudo nmap -sS -p 502,44818,1911,2222,2404 --open <target_IP_range>
(Port 502 = Modbus TCP, 44818 = Ethernet/IP, 1911 = Niagara Fox, 2222 = EtherNet/IP CIP, 2404 = IEC 60870-5-104)
- On Windows, use PowerShell to test connectivity to an ICS device:
Test-NetConnection -Port 502 -ComputerName <ICS_IP>
- For packet analysis, capture Modbus traffic with `tcpdump` (Linux) and filter in Wireshark:
sudo tcpdump -i eth0 port 502 -w modbus_traffic.pcap
Open the capture in Wireshark and apply filter `modbus` to inspect function codes (e.g., 0x01 Read Coils, 0x03 Read Holding Registers).
2. Industrial Control Systems Evaluation (401V)
This course (https://lnkd.in/eEyFeRjb) focuses on evaluating the security posture of an ICS environment, including hands‑on exercises in vulnerability identification.
Step‑by‑step guide for vulnerability assessment:
- After the course, set up a test lab using a virtual ICS simulator like GRFICS (Gas and Refinery Facility ICS) or the open‑source Conpot honeypot.
- On Ubuntu/Debian, install and run Conpot to simulate a vulnerable ICS device:
sudo apt install conpot sudo conpot --template default
- Scan the simulator using Nessus Essentials (free for home use) or OpenVAS. For a quick command‑line check, use `nmap` with ICS‑specific scripts:
nmap --script modbus-discover -p 502 <simulator_IP>
- Windows users can employ the `netstat` command to monitor open ports on a real PLC simulator:
netstat -an | findstr "502"
- Remediate any exposed services by configuring firewall rules. On Linux, use `iptables` to restrict access to port 502:
sudo iptables -A INPUT -p tcp --dport 502 -s <trusted_IP> -j ACCEPT sudo iptables -A INPUT -p tcp --dport 502 -j DROP
- Getting Started in ICS/OT Cyber Security (25+ Hours)
A comprehensive free YouTube series (https://lnkd.in/eyrJufu8) covering everything from basic terminology to incident handling.
Step‑by‑step lab creation:
- Install a hypervisor (VirtualBox or VMware) and deploy a Linux VM (Kali or Parrot) as your attack machine, plus a Windows 10 VM as a management workstation.
- Inside the Kali VM, install `modbus-cli` for interactive Modbus testing:
sudo apt install python3-pip pip3 install modbus-cli modbus-cli <target_IP> 502 read_holding_registers 0 10
- To simulate a PLC, use `pymodbus` library on a separate Ubuntu VM:
sudo pip3 install pymodbus python3 -m pymodbus.server --host 0.0.0.0 --port 502
- Practice discovery with `nmap` and the `modbus-discover` script as shown above. Document findings in a security assessment report.
4. Mastering OT/ICS Cybersecurity with ISA/IEC 62443
This course (https://lnkd.in/e2tmhUH9) aligns with the global standard for ICS security. It covers zone and conduit models, security levels, and risk assessment.
Step‑by‑step implementation of the standard:
- After the training, create a zone/conduit diagram for a sample water treatment plant. Define a “Control Zone” for PLCs and HMIs, and an “Enterprise Zone” for business networks.
- On a Linux firewall (e.g., pfSense or IPFire), implement rules to enforce unidirectional data flow from the control zone to the monitoring zone:
Allow established connections from control zone to enterprise zone sudo iptables -A FORWARD -i eth0 -o eth1 -m state --state ESTABLISHED,RELATED -j ACCEPT Block all new connections from enterprise to control zone sudo iptables -A FORWARD -i eth1 -o eth0 -m state --state NEW -j DROP
- Use Windows Group Policy to restrict USB drives on operator workstations (often a vector for malware like Havex). Run as Administrator:
Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\USBSTOR" -Name "Start" -Value 4
- Validate the zone separation by running an Nmap scan from the enterprise zone against the control zone – it should time out.
5. Intro to OT/ICS Penetration Testing
Free introductory course (https://lnkd.in/erVbZ_yT) that covers reconnaissance, exploitation, and post‑exploitation in ICS contexts.
Step‑by‑step penetration testing exercise (authorized lab only):
- Set up a target ICS simulator (e.g., OpenPLC on a Raspberry Pi or virtual machine). Install OpenPLC on Linux:
git clone https://github.com/thiagoralves/OpenPLC_v3.git cd OpenPLC_v3 sudo ./install.sh
- Use Metasploit to test for default credentials on Modbus devices. Launch
msfconsole:use auxiliary/scanner/scada/modbusdetect set RHOSTS <simulator_IP> set RPORT 502 run
- If the simulator supports it, attempt a Modbus write operation to toggle a coil (e.g., turning off a pump). Using
modbus-cli:modbus-cli <target_IP> 502 write_single_coil 0 0xFF00 Write ON modbus-cli <target_IP> 502 write_single_coil 0 0x0000 Write OFF
- Mitigation: Change default credentials, segment the network, and use Modbus firewalls. On Linux, use `tcp_wrappers` to restrict Modbus access:
echo "modbusd: <attacker_IP>" >> /etc/hosts.deny
6. OSINT (Open Source Intelligence) for ICS/OT
Learn to identify exposed ICS devices without touching the target (https://lnkd.in/gsj4f8hM). Essential for threat intelligence and attack surface mapping.
Step‑by‑step OSINT gathering:
- Install Shodan CLI on Linux (or use the web interface):
sudo apt install shodan shodan init <API_key> shodan search port:502 country:US product:Modbus
- Use Censys to find specific PLC models:
censys search "services.port=502 AND services.service_name=modbus" --index certificates
- For passive reconnaissance, use Google dorks:
intitle:"Rockwell Automation" "FactoryTalk View" -site:rockwellautomation.com inurl:/main.htm "PLC" -site:siemens.com
- Windows users can run `curl` via PowerShell to query Shodan’s API:
$apiKey = "YOUR_API_KEY" curl "https://api.shodan.io/shodan/host/search?key=$apiKey&query=port:44818"
- Analyze exposed devices and report them through responsible disclosure channels. Never attempt unauthorized access.
7. Bonus – Free YouTube Channels & Newsletter
Mike Holcomb’s infographic also points to free YouTube content and a newsletter (https://lnkd.in/ePTx-Rfw). These provide ongoing education and community updates.
Step‑by‑step to stay current:
- Subscribe to the newsletter to receive weekly OT/ICS security tips and new course announcements.
- Follow YouTube playlists that cover hardware hacking (Raspberry Pi PLCs), S7‑1500 hardening, and real‑world incident analysis.
- Join OT/ISC2 or SANS ICS Summits (many free virtual sessions) to complement the courses above.
What Undercode Say:
- Key Takeaway 1: Free, authoritative training from CISA and community experts is readily available – you don’t need expensive SANS courses to start securing critical infrastructure.
- Key Takeaway 2: Hands‑on practice using open‑source tools (nmap, modbus-cli, Shodan, OpenPLC) bridges the gap between theory and real‑world ICS assessment, but always operate in isolated labs.
The scarcity of OT/ICS security talent is well documented, yet these seven courses remove the cost barrier entirely. By combining CISA’s structured curriculum with practical labs – scanning for Modbus, simulating PLCs, and performing OSINT – anyone from IT security generalists to plant operators can gain functional skills. The commands provided above (firewall hardening, packet capture, Metasploit modules) mirror what professionals use in authorized red team exercises. However, the most critical lesson is that ICS environments prioritize safety and availability over confidentiality; never test on live production systems. As more free resources emerge, the gap between IT and OT security will narrow, but hands‑on, ethical application remains non‑negotiable.
Prediction:
Over the next three years, free OT/ICS training will become the primary entry point for new cybersecurity professionals, driven by regulatory mandates (e.g., NIS2, CIRCIA) and the rising tide of ransomware targeting industrial sectors. AI‑powered lab simulators and automated scoring systems will supplement static courses, allowing learners to practice incident response on virtual power grids. Consequently, organizations will shift from relying solely on expensive certifications to validating practical skills via free, community‑driven platforms – democratizing critical infrastructure defense and reducing the global skills gap.
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