The 99% Rule: Why Your OT/ICS Incident Response Plan is Actually an IT War Game + Video

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Introduction:

In the specialized world of Operational Technology (OT) and Industrial Control Systems (ICS) cybersecurity, a hard truth often gets overlooked: despite dealing with PLCs and RTUs, the vast majority of breaches originate in the corporate IT environment. Attackers targeting critical infrastructure rarely start by manipulating a field device; they gain a foothold in a Windows workstation or a Linux server first. Understanding that 99% of incident response is standard IT forensics is the first step in building a resilient defense for the remaining 1% that truly controls the physical process.

Learning Objectives:

  • Understand the “99% Rule” and its implications for OT/ICS incident response preparation.
  • Identify the core open-source and commercial forensic tools used in standard IT environments.
  • Learn practical command-line applications for digital forensics on Windows and Linux systems.
  • Develop a strategy for vendor engagement regarding proprietary OT equipment analysis.

You Should Know:

1. The Core Toolkit: Network and Endpoint Visibility

The foundation of any investigation lies in capturing and analyzing data from standard IT systems. The tools listed in the post are not just suggestions; they are the industry standard for a reason. Here is how to start using them effectively.

  • Network Analysis with Zeek and Wireshark:
  • What it does: Zeek (formerly Bro) acts as a network sensor, logging every connection, DNS query, and HTTP request into structured log files. Wireshark provides deep packet inspection for manual analysis.
  • Step-by-step (Linux):
  1. Install Zeek: `sudo apt-get install zeek` (or build from source).
  2. Configure the monitoring interface: Edit `/etc/zeek/node.cfg` to define the correct interface.
  3. Deploy Zeek: sudo zeekctl deploy. This starts the sensor.

4. Check status: `sudo zeekctl status`.

  1. To capture a specific pcap for analysis with Wireshark: sudo tcpdump -i eth0 -c 10000 -w capture.pcap.
  2. Open the file: wireshark capture.pcap. Use filters like `http.request` or `tcp.port==445` to hunt for malicious traffic.
  • Memory Forensics with Volatility:
  • What it does: Analyzes the RAM of a compromised system to find rootkits, injected code, and processes that don’t exist on the disk.
  • Step-by-step (Windows Memory Dump):

1. Acquire memory using FTK Imager (see below).

  1. Determine the profile of the operating system: volatility -f memory.dump imageinfo.
  2. List running processes at the time of the dump: volatility -f memory.dump --profile=Win7SP1x64 pslist.
  3. Check for hidden processes: volatility -f memory.dump --profile=Win7SP1x64 psscan.
  4. Dump a suspicious process for further analysis: volatility -f memory.dump --profile=Win7SP1x64 procdump -p 1234 -d dumped_process.exe.

2. Acquisition and Triage: KAPE and FTK Imager

Speed is critical during an incident. You need to collect the most volatile data (RAM) and the most relevant forensic artifacts (registry, prefetch, event logs) before the system is turned off.

  • Using FTK Imager (Windows GUI & CLI):
  • What it does: Creates a bit-for-bit forensic image of a drive or captures a memory dump.
  • Step-by-step (Memory Capture):

1. Run FTK Imager as Administrator.

2. Click File > Capture Memory.

  1. Choose a destination path and filename (e.g., D:\evidence\memory.mem).

4. Ensure “Include pagefile” is checked.

  1. Click Capture. This creates the memory dump without shutting down the machine.
  • Using KAPE (Windows CLI):
  • What it does: Kroll Artifact Parser and Extractor (KAPE) is a triage tool that collects and processes files quickly. It’s essential for hunting for IOCs across many machines.
  • Step-by-step (Collection):
  1. Open Command Prompt as Administrator in the KAPE directory.
  2. Run a collection targeting common attacker artifacts: .\kape.exe --tsource C: --tdest D:\KAPE_Output --target !SANS_Triage.
  3. This command targets the source drive C:, sends output to D:\KAPE_Output, and uses the `!SANS_Triage` target to collect prefetch files, recent files, event logs, and more.
  4. To also process the collected files (like parsing timeline data), add the `–module` option, e.g., --module !EZViewer.

  5. Log Aggregation and Hunting: The ELK Stack and Security Onion
    Centralized logging is non-negotiable. If you have to log into every machine individually during an incident, you have already lost. Security Onion is a free and open platform that bundles Zeek, Suricata, and the ELK Stack (Elasticsearch, Logstash, Kibana) for exactly this purpose.

  • Basic ELK Query for Lateral Movement:
  • What it does: Searches for `admin` shares and remote service creation, common techniques for moving from IT to OT environments.
  • Step-by-step (Kibana Query):

1. Navigate to the “Discover” tab in Kibana.

  1. To find remote service creations (a common attacker technique), use a query like: `event_id: 7045 AND service_name: ` (This searches Windows Event ID 7045 for new services).
  2. To hunt for lateral movement using PsExec, search for: process_name: psexec.exe OR process_name: psexesvc.exe.
  3. To find file shares being accessed from the OT network, look for Zeek `smb_files` logs: _index: zeek-smb AND path: \\ipc$.

4. Sysinternals: The Live Response Swiss Army Knife

When dealing with a live, compromised Windows system, having a suite of portable tools is vital.

  • Using Autoruns and Process Explorer:
  • What it does: Identifies persistence mechanisms and verifies signed processes.
  • Step-by-step:

1. Download Sysinternals Suite from the Microsoft website.

2. Run `autoruns64.exe` as Administrator.

  1. Go to Options > Scan Options and check Verify code signatures and Check VirusTotal.com.
  2. Immediately look for entries highlighted in pink or yellow, or unsigned binaries located in user temp folders.
  3. Use `procexp64.exe` (Process Explorer) and check View > Lower Pane View > DLLs to see which DLLs a suspicious process has loaded, looking for unsigned or unusual memory mappings.

5. The 1%: Vendor-Specific OT Forensics

As the post states, the PLCs, RTUs, and DCS controllers require a different approach. You cannot run Volatility on a Siemens S7-1500 PLC. Your preparation must involve direct communication with vendors before an incident.

  • Vendor Engagement Strategy:
  • What it does: Establishes a relationship and access to proprietary forensic tools.
  • Step-by-step:
  1. Inventory: Create a detailed list of all OT/ICS vendors and their specific equipment models (e.g., Rockwell Automation ControlLogix, Schneider Electric Modicon, Siemens PCS 7).
  2. Contact: Reach out to your vendor account representatives or technical support channels.
  3. Request: Specifically ask: “Do you have a forensic toolkit or incident response guide for your controllers? We need tools to capture the runtime logic, last modified times, and current state of the device without causing a fault.”
  4. Practice: Request a demo unit or a virtual environment to practice using these vendor tools so you are familiar with them during a crisis.

What Undercode Say:

  • Key Takeaway 1: Focus your IR training and tooling budgets on Windows and Linux forensics. Mastering tools like KAPE and Volatility will cover 99% of your investigative workload during an OT intrusion.
  • Key Takeaway 2: Treat the 1% of OT-specific devices as a supply chain risk. If you haven’t tested your vendor’s forensic capabilities, you are functionally blind in the process environment. The incident isn’t over just because you cleaned the IT domain; you must validate the integrity of the controllers.
  • Analysis: Mike Holcomb’s distillation of the Mandiant rule serves as a critical wake-up call. The cybersecurity industry often fetishizes the exotic nature of ICS attacks, but the reality is mundane and IT-centric. The most dangerous APT group targeting a power plant is still just using a phishing email to get a credential on a Windows laptop. By acknowledging that your OT incident response is primarily an IT problem, you can stop searching for magic industrial solutions and start hardening the systems that actually get compromised. The tools listed—from Wireshark to the ELK Stack—are mature, well-documented, and staffed by a massive talent pool. Leverage that reality.

Prediction:

As OT environments become increasingly digitized and connected to IT for efficiency gains, the distinction between the two domains will blur. We will see the rise of “Unified Security Operations Centers” where analysts are equally proficient in querying Elasticsearch for IT logs and using vendor-specific APIs to audit PLC ladder logic. The next major evolution will be the development of standardized, open-source forensic tools for proprietary OT protocols, moving the 1% into the 99% and forcing vendors to prioritize security transparency.

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