Analyzing Implicit Interactions to Identify Weak Points in Cyber-Physical System Designs

Cyber-physical systems often consist of many interacting components with numerous communication paths, some of which may be unintended and/or unforeseen by system designers. The existence of such paths, known as implicit interactions, represent security vulnerabilities that can be exploited to mount cyberattacks and destabilize a system. For any system with an abundance of implicit interactions, it can be difficult to understand which aspects of the design contribute most to the presence of this vulnerability. In this paper, we present an approach to identify weak points in the designs of cyber-physical systems based on frequency analyses of the interactions, both implicit and intended, present in a system design. We demonstrate the approach with a real-world Wastewater Dechlorination System. The proposed method can aid system designers in understanding which aspects of their systems contribute most to the existence of implicit interactions to enable effective mitigation strategies to improve overall system security and resilience.