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Introduction:
A joint advisory from the FBI, CISA, NSA, EPA, DOE, and U.S. Cyber Command has confirmed that Iranian-affiliated APT actors are actively exploiting internet-facing Programmable Logic Controllers (PLCs) across multiple U.S. critical infrastructure sectors. These attacks, which have already caused operational disruptions and financial losses, target Rockwell Automation/Allen-Bradley PLCs by manipulating project files and HMI/SCADA display data.
Learning Objectives:
- Understand the specific TTPs and IOCs associated with Iranian-affiliated cyber actors targeting OT environments.
- Learn how to identify and remediate critical vulnerabilities like CVE-2021-22681 in Rockwell Automation PLCs.
- Implement defensive strategies including network segmentation, physical security controls, and continuous monitoring to protect industrial control systems.
You Should Know:
- The “Sam I Am” Threat Model: Why Your PLCs Should Never Go Online
The post’s creative rewrite of Green Eggs and Ham isn’t just entertaining—it’s a perfect allegory for the fundamental rule of OT security: never expose your PLCs to the internet. The CISA advisory confirms this by listing key actions such as removing PLCs from direct internet exposure via secure gateways and firewalls. The adversary does not need advanced zero-days; they simply scan for open ports.
Step‑by‑Step: How to Check for Internet Exposure Using Shodan
Step 1: Navigate to `shodan.io` and create an account.
Step 2: Use the following search queries to identify exposed OT devices:
`port:44818 Rockwell` – Searches for EtherNet/IP devices (common for Rockwell PLCs).
`port:502` – Searches for Modbus TCP devices.
`port:102` – Searches for Siemens S7 communication.
Step 3: Review the results for your organization’s public IP ranges.
Step 4: If you discover an exposed device, immediately disconnect it and implement a secure gateway solution.
2. Architectural Fortification: The DMZ and the Conduit
The poem correctly emphasizes the “plan” involving zones and conduits. This refers to the Purdue Model for Industrial Control Systems, combined with the IEC 62443 standard for zones and conduits. This architecture places PLCs in Level 0/1 (the “danger zone”), the DMZ (Level 3.5) for services, and restricts communication paths to strict conduits.
Step‑by‑Step: Implementing a Basic Conduit with iptables (Linux-based Firewall)
This command blocks all traffic except from a specific trusted engineering workstation (IP: 192.168.1.100) to the PLC (IP: 10.10.10.10).
Flush existing rules iptables -F Set default policies to DROP iptables -P INPUT DROP iptables -P FORWARD DROP Allow traffic from trusted engineer to PLC iptables -A FORWARD -s 192.168.1.100 -d 10.10.10.10 -j ACCEPT Allow established return traffic iptables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
3. Iran’s Cyber Arsenal: Exploiting CVE-2021-22681
The advisory and supporting research highlight the exploitation of CVE-2021-22681, a critical authentication bypass vulnerability in Rockwell Automation Studio 5000 Logix Designer. This vulnerability, which has a CVSS score of 9.8, allows an unauthenticated attacker to bypass verification mechanisms and connect directly to Logix controllers. Crucially, Rockwell has stated this flaw cannot be fixed with a traditional patch, requiring architectural changes instead.
4. Windows Commands for Log Analysis
To hunt for Indicators of Compromise (IOCs) on Windows-based engineering workstations, use these PowerShell commands to check for suspicious network connections on the ports listed in the advisory (44818, 2222, 102, 502).
Check for active connections on suspicious ports
Get-NetTCPConnection -LocalPort 44818,2222,102,502 | Select-Object LocalAddress, LocalPort, RemoteAddress, RemotePort, State
Search Windows Event Logs for failed logins (Event ID 4625)
Get-WinEvent -FilterHashtable @{LogName='Security'; ID=4625} | Select-Object TimeCreated, Message
5. Physical Hardening: The “Run” Mode
The CISA advisory contains a specific, low-tech mitigation: place the physical mode switch on the controller into the Run position. This prevents the remote modification of the project file, which is a primary TTP of the Iranian actors. This is a critical step that cannot be bypassed by software controls alone.
6. Passive OT Network Mapping with GRASSMARLIN
To understand your OT network topology without disrupting operations, use GRASSMARLIN, an open-source passive network mapping tool developed by the NSA. It ingests PCAP files to visually map ICS/SCADA network structures and identify active devices.
Step‑by‑Step: Using GRASSMARLIN
Step 1: Download the latest release from the NSA’s GitHub repository (github.com/iadgov/GRASSMARLIN).
Step 2: Run the GRASSMARLIN JAR file: `java -jar GRASSMARLIN.jar`
Step 3: In the GUI, load a PCAP file captured from a span port on your OT switch.
Step 4: Review the generated topology map to identify unexpected connections or unauthorized devices.
7. Mitigation Commands for Windows Defender Firewall
To immediately block inbound traffic on dangerous ports on Windows-based HMIs or engineering stations, use these netsh commands:
netsh advfirewall firewall add rule name="Block_PLC_Port_44818" dir=in action=block protocol=TCP localport=44818 netsh advfirewall firewall add rule name="Block_PLC_Port_102" dir=in action=block protocol=TCP localport=102 netsh advfirewall firewall add rule name="Block_PLC_Port_502" dir=in action=block protocol=TCP localport=502
What Undercode Say:
- Architecture Over Patches: When a vulnerability like CVE-2021-22681 has no patch, the only defense is a secure architecture (Purdue Model/DMZ). You must assume the PLC is vulnerable and isolate it.
- Iran’s Shift to Kinetic Cyber: The targeting of PLCs indicates a strategic shift from espionage to preparing for disruptive, potentially kinetic, effects on US infrastructure. The “exploitation window” has collapsed to hours.
Prediction:
This advisory marks the beginning of a sustained campaign targeting operational technology. Expect to see similar attacks against other PLC vendors and an increase in AI-assisted reconnaissance, where large language models generate Shodan queries and exploit scripts in minutes. The next wave will likely focus on exploiting supply chain vulnerabilities in OT remote access software, bypassing the DMZ entirely. Organizations that fail to implement the “Zones and Conduits” model now will face inevitable operational disruption within the next 12–18 months.
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Reported By: Rivercaudle Whatyouknowyoulikedit – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
