How can OT operators maintain an OT risk register

Maintaining a robust Operational Technology (OT) risk register is crucial for all organisations that rely on industrial control systems (ICS) and other OT assets. Unlike IT systems, a breach or failure in an OT environment can have catastrophic physical consequences, including safety incidents, environmental damage, and production shutdowns.

As I often say, a well-structured OT risk register isn't just a compliance formality; it's a vital tool for proactively identifying, managing, and mitigating these unique risks. All risk sensitive organisations have to invest in building and maintaining a risk register.

So where do we start? Let’s look at the basics first.

What is an OT Risk Register and Why Maintain It?

An OT risk register is a centralized, living and breathing document that systematically identifies, analyzes, and tracks risks specific to an organization's industrial control systems and operational technology. A risk register is always exclusive to an organisation and is not a replica of something similar built by another organisation.

You can think of it as a comprehensive logbook for all the potential threats to your physical processes and the assets that control them. It serves as a single source of truth for all OT-related risks.

Maintaining an OT risk register is essential for several reasons:

· Proactive risk management: It moves an organization from a reactive stance (dealing with incidents as they happen) to a proactive one (identifying and mitigating risks before they materialize). This is particularly critical in OT, where the cost of an incident is often measured in human lives, environmental impact, or millions of dollars in lost production.

· Prioritization of resources: Not all risks are created (or manifest) equal. The register helps you prioritize threats based on their potential impact and likelihood. So you will know where to allocate limited resources-both financial and human-to the most critical areas.

· Informed decision-making: It provides a clear, data-driven view of your OT risk posture to all stakeholders, from engineers on the factory floor to executives in the C-suite. This shared understanding facilitates smarter decisions about investments in security controls, system upgrades, and policy changes.

· Accountability and ownership: By assigning a "risk owner" to each entry, the register establishes clear accountability. This person or team is responsible for monitoring the risk and ensuring that mitigation strategies are implemented and effective.

· Continuous improvement: A risk register isn't a one-and-done project. Its continuous review process supports an ongoing cycle of risk management, allowing you to adapt to new threats and changes in your operational environment.

A risk register can also help compliment all other OT security measures. It can also serve to hasten risk assessment cycles and contribute to the evolution of a risk-aware workforce.

So how does one go about building an OT register?

Where can one start?

Building an effective OT risk register is a structured process that requires collaboration across different departments, including OT, IT, and business leadership. I know that’s not the answer you are looking for so let me expand and share a few pointed steps.

Here's a step-by-step guide:

Step 1: Get the context right

Before you move away from you desk and start listing risks, you need to define the scope and context. What are you protecting? This involves:

· Asset inventory: Create a comprehensive list of all your OT assets, including programmable logic controllers (PLCs), human-machine interfaces (HMIs), supervisory control and data acquisition (SCADA) systems, and network devices.

· Defining zones and conduits: Following the ISA/IEC 62443 standard, segment your OT environment into logical security zones based on criticality and required security levels. Conduits are the communication pathways between these zones. This segmentation helps you apply targeted security controls.

· Identify business objectives: Understand what's most important to the business. Is it system uptime, data integrity, physical safety, or all of the above? These objectives will help you prioritize risks later.

· Roadmap: A risk register cannot be forgotten once it is created so ensure that you have a way of updating both the risks identified and the context.

Step 2: Identify and describe specific risks

This is the core of the risk register. Gather a diverse group of all stakeholders, including OT engineers, operators, IT security specialists, OEM reps, and business managers, to brainstorm potential risks. Risks should be described in a clear, concise format, including:

· Risk ID: A unique identifier for tracking each risk. This can be an alphanumeric code.

· Risk Description: A clear statement of the risk, e.g., "Unauthorized access to PLC results in a change to the chemical mixing recipe."

· Threat Source: Who or what is the threat? (e.g., external attacker, malicious insider, human error, equipment failure).

· Vulnerability: The weakness that the threat can exploit (e.g., unpatched software, weak passwords, lack of network segmentation).

· Impact: The potential consequence if the risk materializes (e.g., loss of life, environmental damage, production downtime, financial loss).

· Grade: How should the risk be graded based on the impact? Which brings us to the next step

Step 3: Assess and prioritize risks

Once risks are identified, they must be assessed to determine their severity. The most common method is using a risk matrix (also known as a heat map) to plot the likelihood against the impact.

· Likelihood: The probability of the risk occurring (e.g., rare, unlikely, possible, likely, almost certain).

· Impact: The severity of the consequences if the risk happens (e.g., insignificant, minor, moderate, major, catastrophic).

· Map the risks to specific Incident Response steps: To improve the accuracy and impact of Incident Response during an event.

By plotting these on a grid, you can visually determine the inherent risk-the risk level before any controls are applied. The risks that fall into the high-likelihood, high-impact quadrant should be your top priority.

Step 4: Define and document mitigations

For each high-priority risk, you need a plan. Document the following:

· Existing Controls: What measures are already in place to address the risk? (e.g., firewalls, access controls).

· Residual Risk: The risk level that remains after existing controls are considered.

· Mitigation Plan: A clear, actionable plan to further reduce the risk. This might involve implementing new technologies, updating policies, or training staff.

· Risk Owner: The individual or team responsible for implementing the mitigation plan with timelines.

· Target Residual Risk: The desired risk level after the mitigation plan is executed.

How to update and maintain an OT Risk Register

A risk register is a living document, not a static spreadsheet. Effective updating and maintenance is what makes it a powerful tool for continuous risk management. One must always strive to ensure that the data in the document is accurate and as recent as possible. Here are some suggestions on this front:

· Regular reviews: Conduct regular, scheduled reviews of the register. For critical OT environments, this might be monthly or quarterly. The frequency should be based on the dynamic nature of your environment and your risk appetite.

· Continuous monitoring: Use a variety of inputs to keep the register up-to-date. This includes threat intelligence feeds, vulnerability scans, incident reports, and feedback from frontline operators.

· Update and evolve: The register must reflect the current state of your environment. This means adding new risks as new threats emerge, updating the status of mitigation plans, and closing out risks that have been successfully addressed.

· Communicate changes: Ensure that all relevant stakeholders are aware of changes to the risk register, new mitigation plans, and the evolving risk landscape. This communication fosters a strong security culture.

Aligning with IEC 62443 and Other Standards

A key benefit of an OT risk register is its alignment with industry standards and frameworks. The IEC 62443 series is the cornerstone of OT cybersecurity. It's a comprehensive set of standards that provides a structured approach to securing industrial automation and control systems.

· IEC 62443-3-2: Risk Assessment: This part of the standard provides a detailed methodology for conducting an OT risk assessment, which is the foundational process for building your risk register. It guides you on how to define zones and conduits, determine security level targets (SL-T), and identify security requirements.

· Systematic Approach: By following the principles of IEC 62443, your risk register becomes more than just a list of risks; it becomes a structured, auditable document that demonstrates a systematic approach to OT security. It helps you justify security investments and prove due diligence.

· Other Standards: The principles of risk management are universal. Your OT risk register can also be aligned with other frameworks like the NIST Cybersecurity Framework (CSF) and even NIS2, that offer guidance and mandates for managing cybersecurity risk for organizations of all sizes.

How are risk registers linked to risk assessments?

A risk register is a tangible output of your risk management process. This process begins with a formal risk assessment and is guided by your organization's risk appetite.

· Risk Assessment: This is the detailed process of identifying and analyzing risks. The data and findings from your risk assessments-both initial and ongoing-are what populate the risk register. The register is the long-term record of your risk assessment efforts.

· Risk Appetite: This is the level and type of risk an organization is willing to accept to achieve its strategic objectives. Your risk register should be a direct reflection of this. For example, a utility company that provides essential services will have a very low risk appetite for operational downtime, and their register will therefore be highly focused on mitigating those risks. Conversely, a startup might have a higher risk appetite for certain areas to drive innovation. Your risk register is a tool to ensure that your risk exposure stays within your defined appetite.

Compliance factors

The regulatory landscape for OT security is rapidly evolving, particularly for critical infrastructure sectors. An OT risk register is a critical component of a compliance program.

· Mandatory requirements: Many regulations, such as the North American Electric Reliability Corporation's Critical Infrastructure Protection (NERC CIP) standards or Europe's Network and Information Systems (NIS2) Directive, require organizations to perform regular risk assessments and maintain a log of identified risks and their mitigation statuses.

· Audit trail: The risk register serves as a documented audit trail. It provides clear evidence to regulators and auditors that your organization has a structured process for identifying and managing OT risks. This can help you avoid fines and legal penalties in the event of an incident.

· Demonstrating due diligence: In an increasingly litigious environment, a robust risk register can demonstrate that your organization has taken all reasonable steps to protect its OT assets and prevent harm.

To reiterate, an OT risk register is more than just a list of threats; it's a fundamental tool for managing the complexities and unique dangers of the industrial world. By systematically building and maintaining this document with the help of a qualified OT security vendor such as Shieldworkz, you can proactively protect your critical operations, ensure compliance with evolving regulations, and, most importantly, safeguard the physical world that your technology controls. It's an investment in resilience, safety, and operational continuity.

Need help with building your very own OT security risk register? We are here to help. 

Get a free consultation for addressing your OT security challenges.