Abstract
An approach to improve the security of cyber physical systems (CPS) through Intelligent Checkers (IC) is presented. ICs are designed to be behaviorally and structurally independent of the cyber-portion of a CPS and hence not subject to cyber attacks. An IC monitors the status of a physical process and raises an alarm when process measurements violate predefined constraints. A strict one-way communication from an IC to the CPS command center validates the authenticity of the data received from CPS sensors. An IC is able to raise an alarm despite communication failure or undetected cyber attacks. Strategic placement of one or more ICs throughout a CPS is expected to improve the potential for the early detection of attacks.