Design of intelligent checkers to enhance the security and safety of cyber physical systems

An approach for the design and placement of Intelligent Checkers (ICs) is presented along with an application to enhance the security and safety of a water purification system. Each IC, a smart sensor with a one-way outgoing communication over the network, monitors in real-time the status of one or more physical processes and raises an alarm when the monitored process measurements violate predefined constraints. ICs are structurally and behaviorally independent of the cyber-portion of a Cyber Physical System (CPS) and hence are much less likely to be affected by cyber attacks than the control system that monitors and controls a CPS. Thus, ICs serve as devices orthogonal to an existing intrusion detection system and assist in the early detection of successful attacks through independent monitoring of physical processes.