An ICS risk assessment is one of the key steps in securing our ICS environment. Because it allows us to determine our organization’s risk posture, especially in relation to our ICS environment. Some standards, such as IEC 62443, describe the ICS risk assessment framework, which can be used as an internal assessment framework. Below are the steps for performing a proper ICS risk assessment to obtain an objective risk assessment that reflects our existing situation.

Step 1: Define the Scope

The first step is to clearly define the scope of our risk assessment. This includes identifying the boundaries of the ICS, including network infrastructure, devices and software systems relevant to the assessment. It is important to understand what part of the system we are evaluating and what we are trying to protect.

Step 2: Identify Assets and Critical Functions

The next step is we need to identify assets and critical functions within the ICS. Assets include hardware (servers, controllers, etc.) and software components (operating systems, applications, etc.). A critical function is an operation that is essential for the proper functioning of the system. Understanding these assets and features will help us decide what we need to protect.

Step 3: Threat and Vulnerability Assessment

This step assesses potential threats that may affect ICS and identifies vulnerabilities that could be exploited by those threats. Threats can come from a variety of sources, including hackers, malware, and physical incidents. Vulnerabilities can be weaknesses in system design, configuration, and maintenance. A threat and vulnerability analysis helps us understand the potential risks to which our ICS is exposed.

Step 4: Analyzing the Impact

After identifying threats and vulnerabilities, it is important to analyze the possible impact of an attack or incident. When doing so, consider the impact on critical functions, assets, and even our entire organization. For example, an attack on the power grid could disrupt the power supply to homes and businesses. Understanding the results will help us prioritize our risk management efforts.

Step 5: Risk Levelling

With a clear understanding of threats, vulnerabilities and impacts, we can assess risk levels for different scenarios. In this step, each identified threat is assigned a risk level based on its likelihood of occurrence and potential system impact. Risk levels can be categorized as high, medium, or low to identify appropriate risk mitigation strategies.

Step 6: Prioritize the Risk Countermeasures

This step prioritizes actions that can prevent, mitigate or remediate the identified risks. These actions may include implementing security controls, improving system configurations, training staff, improving incident response plans, etc. By focusing on the risks that matter most, we can effectively allocate resources to address the vulnerabilities that pose the greatest threat.

Step 7: Implementation and Monitoring

Once corrective actions have been identified, implement them and continuously monitor the effectiveness of security measures. Regular monitoring and testing ensure that implemented controls are working as intended and that new vulnerabilities and threats are identified in a timely manner. 

Step 8: Review and Update

Finally, it is important to regularly review and update the risk assessment to reflect changes in the ICS environment. As technology advances and new threats emerge, risk assessments need to be revised and kept up to date. This is an ongoing process and requires constant attention to ensure ICS security.

An ICS risk assessment is a comprehensive process that helps us understand the potential risks faced by our industrial control (ICS)/operational technology (OT) system. This allows us to take appropriate proactive measures to protect your environment based on our risk situation. It also helps to prioritize countermeasures depending on the situation.