FREE 25-Hour OT/ICS Cybersecurity Course: 110,000+ Students Can’t Be Wrong – Master Industrial Control Systems Security Now! + Video

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Introduction:

Operational Technology (OT) and Industrial Control Systems (ICS) cybersecurity is a specialized field protecting critical infrastructure like power grids, water treatment plants, and manufacturing lines. Unlike traditional IT security, OT prioritizes safety and availability over confidentiality, making common IT security practices potentially disruptive. With attacks like Colonial Pipeline and Ukraine’s power grid breaches, hands-on skills in asset inventory, protocol analysis, and secure architecture are no longer optional – they are essential for any cybersecurity professional.

Learning Objectives:

  • Understand the core differences between IT and OT environments, including the Purdue Model for secure network architecture.
  • Perform threat and vulnerability management, OSINT gathering, and incident detection specific to ICS protocols like Modbus, DNP3, and S7.
  • Apply practical penetration testing techniques and review industry standards (NIST SP 800-82, IEC 62443) to harden real-world OT assets.

You Should Know:

  1. Mapping Your OT Network with GRASSMARLIN (Asset Inventory & Network Segmentation)

GRASSMARLIN is a free passive network mapping tool from NSA that visualizes ICS/OT network traffic without disrupting operations. It helps create an asset register – a key requirement from Mike Holcomb’s course.

Step‑by‑step guide:

  • Download GRASSMARLIN from GitHub (Windows executable available).
  • Capture a PCAP file of your OT network traffic using tcpdump (Linux) or WireShark.
  • Linux command: `sudo tcpdump -i eth0 -s 65535 -w ot_traffic.pcap`
    – Windows (using npcap): `pktmon start –capture –pkt-size 0 –file-name ot_capture.etl` (then convert to pcap)
  • Open GRASSMARLIN, click “Add PCAP” and load your file. The tool will automatically discover devices, protocols (Modbus/TCP, S7comm, DNP3, etc.), and communication flows.
  • Export the asset register as CSV. Use it to identify rogue devices or unexpected connections.
  • Compare findings against the Purdue Model – ensure no direct IT-to-controller paths.
  1. Scanning OT Networks Safely with Nmap and Modbus Scripts

Aggressive scanning can crash legacy PLCs. Use safe options and ICS‑specific NSE scripts.

Step‑by‑step guide:

  • Install Nmap on Linux: `sudo apt install nmap`
    – Use a slow, connectionless scan: `nmap -sS -p 502 –script modbus-discover –script-args=’modbus-discover.aggressive=false’ –max-retries 1 –min-rate 10 `
    – Port 502 = Modbus/TCP; other common ports: 102 (S7), 20000 (DNP3), 44818 (CIP).
  • For Windows, use Zenmap GUI with same arguments.
  • Interpret results: A successful `modbus-discover` may return slave IDs and device info. Never write to holding registers during scanning.
  • Mitigation: Implement firewall rules to allow only authorized scanners and disable unused protocols.
  1. OSINT for Industrial Controls – Shodan & Censys

Attackers use search engines for internet‑facing OT devices. Learn to find your own exposure ethically.

Step‑by‑step guide:

  • Go to Shodan.io (free account). Use filters: `port:502` country:"US" "Modbus".
  • For ICS/OT specific: `”S7-1200″` or "Allen-Bradley".
  • On Linux, install `shodan` CLI: pip install shodan, then shodan init <API_KEY>.
  • Run: `shodan search –limit 10 –fields ip_str,port,org,product port:44818`
    – Use `shodan download` to grab a dataset for offline analysis.
  • Mitigation: Use allowlists and VPNs; never expose OT devices directly to the internet. Run regular scans of your public IP ranges.
  1. Incident Detection – Monitoring Modbus Traffic with Wireshark and Snort

Detecting malicious writes or unexpected function codes is critical. Set up a simple IDS rule.

Step‑by‑step guide:

  • Capture live OT traffic: `sudo wireshark -i eth0 -f “tcp port 502″`
    – Apply display filter: `modbus.func_code == 5` (write single coil) or `modbus.func_code == 16` (write multiple registers). Highlight abnormal write commands from non‑HMIs.
  • For persistent detection, install Snort on a span port.
  • Linux: `sudo apt install snort`
    – Add rule to /etc/snort/rules/local.rules:

    alert tcp $HOME_NET 502 -> any any (msg:"Modbus write coil"; content:"|05|"; depth:1; sid:1000001;)
  • Test with: `sudo snort -A console -q -c /etc/snort/snort.conf -i eth0`
    – Windows alternative: Use Security Onion (virtual appliance) with Zeek and ELK stack.

5. Hardening Windows Workstations in an OT Environment

OT workstations often run legacy Windows (7, XP). Limited patching, but you can apply mitigating controls.

Step‑by‑step guide:

  • Disable unnecessary services: `sc config RemoteRegistry start= disabled` (Command Prompt as admin).
  • Enable Windows Firewall for inbound rules only – allow only specific HMIs and engineering laptops. 
    netsh advfirewall firewall add rule name="Block_All_Inbound" dir=in action=block
netsh advfirewall firewall add rule name="Allow_HMI" dir=in action=allow protocol=TCP localport=102 remoteip=192.168.1.50
  • Use AppLocker to whitelist approved executables (PowerShell: Get-AppLockerPolicy).
  • Disable AutoRun: `reg add HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer /v NoDriveTypeAutoRun /t REG_DWORD /d 255 /f`
    – Implement local account restrictions: `net user guest /active:no` and enforce strong passwords for local admins.
  1. Penetration Testing ICS Protocols Using Modbus-cli and Python

Learn safe exploitation with free tools – only on your own lab or explicit permission.

Step‑by‑step guide (Linux lab environment):

  • Install modbus-cli: `sudo gem install modbus-cli`
    – Read coil status: `modbus read 192.168.1.100 502 1 0 10` (reads coils 0‑9)
  • Write to a single coil (use only in test lab): `modbus write 192.168.1.100 502 1 0 1` (writes ON to coil 0)
  • For Python automation: 
    from pyModbusTCP.client import ModbusClient
client = ModbusClient(host="192.168.1.100", port=502, auto_open=True)
client.write_single_coil(0, True)
  • Mitigation: In production, deploy deep packet inspection (DPI) firewalls that block unauthorised writes, and keep a separate test network.
  1. Reviewing Industry Standards – NIST SP 800-82r3 in Practice

NIST SP 800-82 provides 130+ controls. Pick three quick wins for your environment.

Step‑by‑step guide:

  • Control IA-5 (authenticator management): Implement multi‑factor authentication for remote access to OT using a jump server.
  • Control SC-7 (boundary protection): Use a dual‑firewall architecture per the Purdue Model (Levels 3.5/4). Example iptables on Linux jump host: 
    iptables -A FORWARD -i eth0 (corporate) -o eth1 (OT) -j DROP
iptables -A FORWARD -i eth1 -o eth0 -m state --state ESTABLISHED,RELATED -j ACCEPT
  • Control SI-4 (system monitoring): Deploy a passive Network Security Monitoring sensor with Zeek. Command to extract Modbus requests: 
    zeek -r ot_traffic.pcap protocols/modbus/package.zeek
cat conn.log | grep modbus
  • Document compliance gaps and remediate in priority order (access control first).

What Undercode Say:

  • Key Takeaway 1: Free, high‑quality OT/ICS training exists – Mike Holcomb’s 25‑hour course on YouTube (https://lnkd.in/eif9fkVg) has already helped over 110,000 learners. Pair it with active lab work using the commands above.
  • Key Takeaway 2: OT security is not “IT security for factories”. Success requires understanding protocols (Modbus, DNP3, S7), passive asset discovery, and safe scanning. The 11‑part structure of the course – from OSINT to penetration testing – provides a complete roadmap.

The analysis: The post highlights a critical skills gap: IT professionals often lack OT context, and traditional security tools can disrupt operations. By distributing a structured, free course and supplementary articles (like Ishan Shah’s key takeaways), the community is lowering the entry barrier. The most practical value comes from bridging theory (Purdue Model, standards) with hands‑on techniques (GRASSMARLIN, snort rules, modbus-cli). As more energy, water, and manufacturing sectors digitize, demand for practitioners who can apply these exact commands – safely – will skyrocket. This isn’t just certification preparation; it’s operational resilience.

Prediction:

Over the next 18 months, attacks on OT will shift from opportunistic (e.g., ransomware in IT networks spreading accidentally) to targeted sabotage via supply chain compromise and AI‑generated attack scripts. Consequently, regulatory bodies (CISA, ENISA, and national grid operators) will mandate annual hands‑on simulations and passive monitoring for all critical infrastructure. Professionals who complete courses like this and document practical lab exercises (using the steps above) will command premium salaries, while organizations that neglect OT hygiene will face operational blackouts and six‑figure fines. The free → paid course model will accelerate, with YouTube becoming the primary delivery channel for OT security upskilling – making verified, command‑level tutorials more valuable than ever.

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