Detectability of Cooperative Zero-Dynamics Attack

This paper studies the detectability of cooperative zero-dynamics attacks, in the context of coupled harmonic oscillators. A defense strategy, which consists of a strategic topology switching and a strategic output observing, is proposed. The primary advantages of the defense strategy are threefold: (i) in achieving synchronization in the absence of attacks, it simplifies the control protocol to use the relative position measurements, while it has no constraint on the magnitude of coupling weights; (ii) in revealing cooperative zero-dynamics attack, it has no constraints on the number of observed outputs, while allowing the defender to have no knowledge of the attack-starting time and the oscillators under attack; (iii) it deprives the undetectable cooperative zero-dynamics attack's ability of altering steady-state value and affecting system stability. Simulations are provided to verify the effectiveness of the defense strategy.