FREE 25-Hour ICS/OT Security Course & 50+ Hours of Zero-Cost Training – Your Ultimate 2026 Playbook + Video

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Introduction:

Industrial Control Systems (ICS) and Operational Technology (OT) environments were historically air-gapped, but convergence with IT and cloud connectivity has exposed critical infrastructure to ransomware and state-sponsored attacks. The post above, shared by a top cybersecurity influencer, compiles an all-in-one free resource list – including a 25-hour course, 200+ review questions, and a dedicated YouTube channel – to help professionals bridge the gap between traditional IT security and ICS/OT defense without spending a dollar.

Learning Objectives:

  • Understand core ICS/OT architectures, protocols (Modbus, DNP3, IEC 61850), and the Purdue Model.
  • Access and utilize free training courses, eBooks, and newsletters for both IT-security and OT-engineering backgrounds.
  • Apply practical Linux/Windows commands, Nmap scripts, and Shodan filters to assess and harden OT network perimeters.

You Should Know:

  1. Getting Started with Industrial (ICS/OT) Cyber Security – Free Course & eBooks

The post provides a 25+ hour course (https://lnkd.in/eJBm-B_f) and two targeted eBooks (https://lnkd.in/e8GfQW3n): one for IT-security professionals (focus on network segmentation, firewalls, and DIACAP) and one for OT/engineering backgrounds (focus on PLC logic, HMI security, and physical process awareness).

Step‑by‑step guide to access and use:

  • Step 1: Click the shortened links – they redirect to official platforms (e.g., UtilSec’s website or YouTube).
  • Step 2: Download the eBooks as PDFs; open them in a reader. For IT background, start with “Chapter 3: Zones and Conduits.” For OT background, begin with “Chapter 5: Modbus Vulnerabilities.”
  • Step 3: Enroll in the 25-hour course (free). Watch modules 1–4 for architecture, then module 7 on threat modeling.
  • Step 4: Complement with the YouTube channel (youtube.com/@utilsec) – 50+ hours of free content. Search for “PLC programming security” or “ICS incident response walkthrough.”

Linux command to scan for exposed Modbus (TCP/502):

nmap -p 502 --script modbus-discover <target-IP>

Windows PowerShell command to check for suspicious Modbus traffic: 

Get-NetTCPConnection -LocalPort 502 | Where-Object {$_.State -eq "Listen"}

2. Mastering ISA/IEC 62443 – Framework Hardening Steps

The ISA/IEC 62443 course (https://lnkd.in/e2tmhUH9) is referenced as a free resource. This standard defines security levels (SL1 to SL4) and zone/conduit models.

Step‑by‑step guide to apply a key control (patch management in OT):
– Step 1: Define zones (e.g., Control Zone, Safety Zone) and conduits (network pathways).
– Step 2: For each asset (PLC, RTU, HMI), map the current security level against SL2 requirements (minimum for industrial).
– Step 3: Use the free 200+ ICS/OT review questions (https://lnkd.in/ecxKkkXE) to test understanding of 62443-3-3 (system requirements).
– Step 4: Implement network segmentation: On a Linux jump host, block inter-zone traffic with iptables: 

iptables -A FORWARD -s 192.168.1.0/24 -d 192.168.2.0/24 -j DROP

– Step 5: For Windows-based HMIs, disable unused services and apply application whitelisting via AppLocker (Windows Security → AppLocker → Executable Rules).

3. OT/ICS Penetration Testing – Introduction to Tooling

The “Introduction to OT/ICS Penetration Testing” course (https://lnkd.in/e2EPEDet) teaches passive and active reconnaissance.

Step‑by‑step guide to passive OT discovery (no disruption):

  • Step 1: Use Wireshark on a mirrored SPAN port of an OT switch. Filter for Modbus (tcp.port==502) or DNP3 (tcp.port==20000).
  • Step 2: Run a Linux script to enumerate function codes from captured PCAP: 
    tshark -r capture.pcap -Y "modbus.func_code" -T fields -e modbus.func_code | sort | uniq -c
  • Step 3: For active testing in a lab environment, use `modbus-cli` (install via pip install modbus-cli): 
    modbus read-holding-registers <PLC-IP> 0 10
  • Step 4: To harden against such scans, set up a Modbus firewall on the gateway: block write commands (function codes 5, 6, 15, 16) while allowing read-only (function codes 1,2,3,4).

Linux iptables example (prevent Modbus writes):

iptables -A INPUT -p tcp --dport 502 -m string --string "\x05" --algo bm -j DROP
  1. Weekly Newsletter & Community Group – Staying Current

Join over 6,900+ others via the newsletter (https://lnkd.in/gsYk_gtv) and the Telegram/LinkedIn community (https://lnkd.in/g87eEGqw).

Step‑by‑step to automate newsletter threat intel:

  • Step 1: Subscribe with your email. Each week, you get 3–5 short bulletins on new ICS vulnerabilities (e.g., CVE-2025-XXXX for Rockwell Automation).
  • Step 2: Create a folder in Outlook/Gmail and set a rule: “Subject contains ‘ICS/OT Weekly’ → move to ‘OT_Intel’ folder.”
  • Step 3: Use a Python script to parse saved emails for CVE IDs and feed them into your SIEM: 
    import imaplib, re
mail = imaplib.IMAP4_SSL("imap.gmail.com")
mail.login("your-email", "app-password")
... extract CVEs and print
  1. Infographics & Review Questions – Quick Reference for Audits

All infographics in one place (https://lnkd.in/eKzqBF7M) cover Purdue Model, SANS ICS attack lifecycle, and protocol headers. The 200+ review questions (link above) mimic CISSP-ISSAP or GICSP exam style.

Step‑by‑step to use them for team training:

  • Step 1: Download infographics – print and post in control room for shift handovers.
  • Step 2: Run a weekly 10-question quiz from the 200+ set using a free tool like Kahoot or even a shared Google Form.
  • Step 3: For each wrong answer, reference the 25-hour course timestamp (e.g., “Wrong on Modbus exception codes → watch Module 8 at 34:20”).

Windows command to quickly share review questions across a domain: 

Copy-Item "\share\ICS_Questions.pdf" -Destination "C:\Users\Desktop\" -Recurse

What Undercode Say:

  • Free, curated resources remove the entry barrier for ICS/OT security – no expensive SANS courses needed to start.
  • The split eBooks (IT vs. OT background) acknowledge a critical reality: IT pros need process awareness, while OT engineers need threat modeling and network segmentation skills.
  • The 200+ review questions and infographics turn passive learning into active recall, essential for certifications like GICSP or IEC 62443 Associate.
  • Combining the YouTube channel (50+ hours) with the 25-hour course gives over 75 hours of structured, no-cost training – comparable to a university module.
  • The newsletter with 6,900+ subscribers indicates a growing community; leveraging shared intel can preempt attacks like the 2025 water treatment plant breaches.

Prediction:

By 2027, nation-state attacks on OT will shift from disruptive (ransomware) to destructive (safety system manipulation). Free resources like those listed will be the primary upskilling method for mid-tier engineers, but organizations that fail to implement ISA/IEC 62443-based zone conduits will face catastrophic failures. Automated OT patch validation using containerized testbeds (e.g., Docker with OpenPLC) will become mandatory, and the demand for professionals who have completed these free courses will outstrip supply – driving salary premiums of 35% over generic IT security roles. Expect LinkedIn to introduce “OT Security Pathway” badges based on such community-driven resources, and regulators will reference free course completion as a compliance “due diligence” factor in critical infrastructure audits.

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