Securing cyber-physical systems with adaptive commensurate response

Cyber-Physical Systems (CPSs) are ubiquitous in power systems, transport and medical systems, and critical infrastructures. Current protocols and applications allow significant changes to a system to take place within a short time or small network footprint, which can be exploited by attackers to cause a great impact on the physical systems. This paper proposes adaptive Commensurate Response (CR) to narrow down the asymmetry between the cost of attacks and their impact through enforcing command footprints to be commensurate with their impact on the system. Such impact is measured by the change of the setpoint (change-driven CR) or the distance between the operating state and the critical state (criticality-driven CR). Change-driven CR is effective for setpoint attacks with big setpoint changes, and criticality-driven CR can be used to combat both setpoint attacks and actuation attacks. Our case study on automobile cruise control demonstrates that CR can effectively improve the system resilience and attack survivability while satisfying QoS requirements.