CHASE – Visualizing cyber security vulnerabilities using bowties

Hazards 29 is Europe’s leading process safety forum.

At this year’s event, industry expert Andy Geddes and CGE Partner David Hatch from Process Safety Integrity presented their new CHASE concept. Their work has developed a practical methodology for Computer Hazard And Security Evaluation.

You can’t defend what you don’t understand

Cyber security is a major concern across all industries with the threat of data theft or corruption, disabled functionality such as denial of service or ransomed ware, or spurious protection activation. With limited resources, organizations must target their cyber security efforts wisely and proportionally to prevent, detect, and recover from intentional attacks and unintentional challenges.

Plant and equipment need robust security to defend against deviations within Industrial Automation Control Systems (IACS) and incursions into IT systems such as maintenance management or enterprise resource planning systems. As the UK’s Health and Safety Executive says: “In order to defend a system, it is first important to know what is to be defended”. They stress that “you can’t defend what you don’t understand” (HSE OG0086).

Physical & logical topology

CHASE starts by creating a topological map of the physical plant and logical IACS assets that is clear and concise. All control and protection measures (subdivided into Zones and Conduits) are overlaid onto the map with a view of potential hazards, which could result in major accidents (MA) and/or loss of essential services (LES). This technique responds to the current focus of the competent bodies including the UK’s Health and Safety Executive (HSE) and Cyber Security Centre (CSC). The mapping and evaluation also consider environmental impact and commercial or reputational damage. CHASE uses the concept of vulnerability to infer likelihood because the ecology of cyber-attacks is constantly evolving. Vulnerability is combined with asset hazard (MA or LES) severity to generate a high-level risk assessment.

High-level risk assessment

CHASE uses bowties to visualize the high-level risk assessment by presenting reasonably foreseeable threats (e.g. OG0086 Table 5.1) and their countermeasures or barriers. This allows the applicability of the threat and the adequacy of the barriers to be risk assessed.