Stealthy deception attacks for cyber-physical systems

We study the security of Cyber-Physical Systems (CPS) in the context of the supervisory control layer. Specifically, we propose a general model of a CPS attacker in the framework of Discrete Event Systems (DES) and investigate the problem of synthesizing an attack strategy for a given controlled system. Our model captures a class of deception attacks, where the attacker has the ability to modify a subset of sensor readings and mislead the supervisor, with the goal of inducing the system into an undesirable state. We introduce a new type of a bipartite transition structure, called Insertion-Deletion Attack structure (IDA), to capture the game-like interaction between the supervisor and the environment (which includes the system and attacker). This structure is a discrete transition system that embeds information about all possible attacker's stealthy actions, and all states (some possibly unsafe) that become reachable as a result of those actions. We present a procedure for the construction of the IDA and discuss its properties. Based on the IDA, we discuss the characterization of successful stealthy attacks, i.e., attacks that avoid detection from the supervisor and cause damage to the system.