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Introduction:
Operational Technology (OT) and Industrial Control Systems (ICS) – the backbone of power grids, water treatment, and manufacturing – face an unprecedented wave of cyber threats. With attackers leveraging AI to automate vulnerability discovery and adversary-in-the-middle attacks on legacy protocols like Modbus and DNP3, defenders must rapidly upskill. A newly released 2026 free course by Mike Holcomb provides labs, hacking tools, and AI-focused updates to secure these environments, bridging the gap between IT security and industrial physical processes.
Learning Objectives:
– Identify and enumerate OT/ICS attack surfaces using passive and active reconnaissance techniques.
– Implement AI-driven anomaly detection and firewall hardening to mitigate Modbus/TCP abuse.
– Execute a complete incident response simulation for a compromised PLC, including forensic acquisition and recovery.
You Should Know
1. Mapping OT/ICS Attack Surfaces with Shodan and Nmap
Before defending, you must see what attackers see. Industrial devices are often exposed via default credentials or misconfigured firewalls. This step‑by‑step guide leverages OSINT and network scanning to inventory your ICS perimeter.
Step‑by‑step guide:
1. Shodan search for exposed ICS devices
Use Shodan’s web interface or CLI to find Modbus (port 502), Siemens S7 (port 102), or BACnet (port 47808) devices.
Install Shodan CLI (Linux/macOS) pip install shodan shodan init YOUR_API_KEY Search for Modbus devices in a specific country shodan search port:502 country:"US" --limit 10
2. Passive reconnaissance with Nmap
Use the `ics` NSE scripts to enumerate PLCs without crashing them (avoid aggressive scans).
nmap -sV -p 502 --script modbus-discover 192.168.1.0/24
3. Windows alternative: use Zenmap GUI
Run the same command via Zenmap, saving outputs for compliance reporting.
4. Interpret results
Look for vendor strings, Siemens CPU types, or Rockwell Automation fingerprints. Each exposed device is a potential entry point for ransomware.
2. Securing Modbus/TCP Communications with Firewall Rules and Deep Packet Inspection
Modbus/TCP has no authentication or encryption by default. Attackers can write to coils (digital outputs) and cause physical damage. Hardening requires network segmentation and active packet filtering.
Step‑by‑step guide:
1. Restrict Modbus traffic to authorized HMIs only
On a Linux gateway (e.g., Raspberry Pi running iptables):
Allow Modbus only from specific HMI IP 10.0.0.50 iptables -A INPUT -p tcp --dport 502 -s 10.0.0.50 -j ACCEPT iptables -A INPUT -p tcp --dport 502 -j DROP iptables -A OUTPUT -p tcp --sport 502 -d 10.0.0.50 -j ACCEPT iptables -A OUTPUT -p tcp --sport 502 -j DROP
2. Windows Defender Firewall rule (PowerShell as Admin)
New-1etFirewallRule -DisplayName "Block Modbus except HMI" -Direction Inbound -Protocol TCP -LocalPort 502 -RemoteAddress 10.0.0.50 -Action Allow New-1etFirewallRule -DisplayName "Block all other Modbus" -Direction Inbound -Protocol TCP -LocalPort 502 -Action Block
3. Deep packet inspection with `modbus-cli`
Monitor for illegal function codes (e.g., function 0x06 write single register from an untrusted source):
Use tcpdump to capture traffic and send to custom analyzer tcpdump -i eth0 -1 port 502 -w modbus_capture.pcap Analyze with modbus-cli (install via pip) modbus-cli pcap --file modbus_capture.pcap --alert "function 6"
3. Leveraging AI for Anomaly Detection in Industrial Networks
Traditional signature‑based IDS fails against novel zero‑day attacks. AI models trained on normal ICS traffic patterns can flag deviations such as unexpected command sequences or abnormal register reads.
Step‑by‑step guide:
1. Collect baseline traffic using Zeek (formerly Bro)
Install Zeek on Ubuntu 22.04
sudo apt install zeek
Enable Modbus analyzer
echo "redef Modbus::default_register_map += { [ 1 ] = 40001 }; " >> /opt/zeek/share/zeek/site/local.zeek
zeek -i eth0 -C
2. Train a simple LSTM model (Python)
Use extracted features: packet length, inter‑arrival time, function codes.
import numpy as np
from sklearn.ensemble import IsolationForest
Example feature array: [func_code, register_addr, value_len]
X_train = [[1,40001,2], [3,40002,2], [1,40001,2], [16,0,10]]
model = IsolationForest(contamination=0.1)
model.fit(X_train)
Detect anomaly: write to coil from unknown source
anomaly = model.predict([[5,0,1]]) function 5 = write single coil
print("Anomaly detected!" if anomaly == -1 else "Normal")
3. Deploy as real‑time alert
Pipe Zeek logs to the model and trigger a SIEM alert when deviation exceeds threshold.
4. Hands‑On Lab: Simulating a PLC Exploit and Mitigation using OpenPLC
Theory becomes skill only through practice. OpenPLC is a free, open‑source programmable logic controller emulator that runs on Linux/Windows and supports Modbus, DNP3, and BACnet.
Step‑by‑step guide:
1. Install OpenPLC
git clone https://github.com/thiagoralves/OpenPLC_v3.git cd OpenPLC_v3 sudo ./install.sh Start the web interface (default: http://localhost:8080) sudo ./start_openplc.sh
2. Upload a vulnerable ladder logic (e.g., tank level control without authentication)
Use the built‑in editor or upload a `.st` (Structured Text) file.
3. Exploit via Metasploit Modbus auxiliary
msfconsole use auxiliary/scanner/scada/modbusclient set RHOSTS 127.0.0.1 set ACTION WRITE_COIL set DATA 1 set COIL_NUMBER 0 run
The PLC coil toggles – simulating an attacker opening a drain valve.
4. Mitigation
Add a `modbus_filter` layer using OpenPLC’s built‑in Access Control List (ACL):
– Edit `/opt/openplc/webserver/core/modbus_server.py`
– Uncomment `MODBUS_ALLOWED_IPS = [‘192.168.1.100’]`
– Restart the server. Only that HMI can write coils.
5. Hardening Remote Access for OT/ICS (VPN, Jump Hosts, MFA)
Remote maintenance ports are the most common initial attack vector (e.g., Colonial Pipeline). Replace direct RDP or TeamViewer with a hardened jump host + two‑factor authentication.
Step‑by‑step guide:
1. Deploy a WireGuard VPN on a dedicated Linux jump host
Install WireGuard on Ubuntu 22.04 sudo apt install wireguard cd /etc/wireguard umask 077; wg genkey | tee privatekey | wg pubkey > publickey Create config wg0.conf with [bash] entries for each engineer
2. Enforce MFA using `google-authenticator` on the jump host
sudo apt install libpam-google-authenticator google-authenticator -t -f -d -r 3 -R 30 -w 3 Edit /etc/pam.d/sshd: add 'auth required pam_google_authenticator.so'
3. Restrict SSH access to authenticated users
/etc/ssh/sshd_config ChallengeResponseAuthentication yes AuthenticationMethods publickey,keyboard-interactive
4. Windows hardened jump host (using PowerShell)
Install OpenSSH server, then set MFA via Duo or Azure AD Application Proxy Add-WindowsCapability -Online -1ame OpenSSH.Server~~~~0.0.1.0 New-ItemProperty -Path "HKLM:\SOFTWARE\OpenSSH" -1ame "DefaultShell" -Value "C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe" -Force
6. Incident Response Playbook for ICS Ransomware
When ransomware hits a human‑machine interface (HMI) and stops the production line, you have minutes to isolate without damaging physical equipment.
Step‑by‑step guide:
1. Immediate physical/network isolation
– Linux gateway: `sudo ifconfig eth0 down` (stop all OT traffic)
– Windows HMI: `netsh advfirewall set allprofiles firewallpolicy blockinbound,blockoutbound`
2. Forensic acquisition of the HMI
Linux live response sudo dd if=/dev/sda of=/mnt/forensics/hmi_drive.dd bs=4096 status=progress Collect running processes ps auxwf > process_list.txt
Windows PowerShell (Admin)
Get-Process | Export-Csv -Path C:\forensics\processes.csv Get-Service | Export-Csv -Path C:\forensics\services.csv
3. Check for modified ladder logic
Retrieve last known‑good configuration from backup PLC and compute checksums:
sha256sum /opt/openplc/scripts/current_program.st > current_checksum.txt sha256sum /backup/known_good.st > good_checksum.txt
4. Restore from air‑gapped backup
Use a clean laptop to flash the original firmware and ladder logic to the PLC via vendor software (e.g., Siemens STEP 7 safety mode).
7. Continuous Learning Resources from the Free Course
Mike Holcomb’s 2026 course is a living repository. Extract and use the following URLs to build your own lab:
– Main course playlist – `https://lnkd.in/gyKC8vPC` (YouTube, first part now live)
– Free video series – `https://lnkd.in/eif9fkVg` (short, focused OT/ICS topics)
– Newsletter (8,100+ subscribers) – `https://lnkd.in/ePTx-Rfw` (weekly updates on AI in OT/ICS)
How to use them:
– Clone the YouTube videos using `yt-dlp` for offline lab access:
yt-dlp -f bestvideo+bestaudio --merge-output-format mp4 https://lnkd.in/gyKC8vPC
– Review the slides and infographics – they include firewall cheat sheets and Modbus function code maps.
– Practice with the provided hacking tools (e.g., `s7‑200‑bruteforce`, `modbus‑fuzzer`) inside a virtualized ICS environment (e.g., GRFICS, FactoryIO).
What Undercode Say:
– Key Takeaway 1: The convergence of AI with OT/ICS attack tools means defenders can no longer rely on air gaps or obscurity; they must implement active monitoring and machine learning‑based anomaly detection at the protocol level.
– Key Takeaway 2: Free resources like Holcomb’s course lower the barrier to entry, but real‑world readiness requires hands‑on lab work – running OpenPLC, writing firewall rules, and simulating ransomware responses.
Analysis: The 2026 update highlights a critical shift: AI is now a double‑edged sword. Attackers use LLMs to generate custom Modbus payloads, while defenders leverage small‑footprint models on edge gateways. The course’s inclusion of review questions and hacking tools bridges the gap between theory and practice. However, the most valuable component is the lab infrastructure – without it, learners gain only conceptual knowledge. The newsletter also provides a sustainable update path as threats evolve. One missing element is cloud‑native OT (e.g., Azure IoT Edge for industrial devices); future iterations should cover API security for cloud SCADA. Overall, this is an essential starting point for IT pros transitioning into OT security.
Prediction:
– -1 Over the next 12 months, AI‑generated spear‑phishing targeting OT engineers will increase by 200%, bypassing traditional email filters and leading to credential theft for remote access gateways.
– -1 Legacy PLCs running Windows CE or VxWorks without patch support will become prime ransomware targets, with attackers leveraging automated Shodan scanners – the free course’s mapping techniques will be used offensively as well.
– +1 Widespread adoption of free OT/ICS training will produce a new generation of defenders who understand both Modbus internals and AI anomaly detection, reducing mean time to detect (MTTD) from weeks to hours.
– +1 Regulatory bodies (e.g., CISA, ENISA) will integrate AI‑powered ICS forensics into mandatory incident reporting, using the same open‑source tools taught in the course to standardize response across critical infrastructure sectors.
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