Enhanced Anomaly Detector for Nonlinear Cyber-Physical Systems against Stealthy Integrity Attacks

Abstract

The detection of stealthy integrity attacks for nonlinear cyber-physical systems is a great challenge for the research community. This paper proposes a backward-in-time detection methodology to enhance the anomaly detector against stealthy integrity attacks for a class of nonlinear cyber-physical systems. It uses the virtual value of the state at a time instant prior to the occurrence time of the attacks for detecting stealthy attacks. The definition of stealthy integrity attacks is formulated in the context of nonlinear plants such that they are undetectable with respect to traditional anomaly detectors. A H∞ fixed-point smoother is developed for estimating the analytical virtual values of the states at a prior time to the attack occurrence time, and then, the backward-in-time detection schemes are proposed based on the smoother. Based on the prior estimates, attack residual generation and threshold generation schemes are designed. Finally, a simulation is presented to illustrate the effectiveness of the enhanced anomaly detector.