Abstract
Recent studies have considered thwarting false data injection (FDI) attacks against state estimation in a power grid by proactively perturbing branch susceptances. The approach is known as moving target defense (MTD). However, the effectiveness of MTD has not been thoroughly analyzed in the existing literature. In this paper, we prove that, despite of the deployment of MTD, it is possible for the attacker to launch stealthy FDI attacks if the number of branches l of the power system is less than twice the number of system states n (i.e., l < 2n, where n + 1 is the number of buses) based on the DC power flow model. Moreover, MTD has the complete capability to detect any FDI attacks with the form a = H c only if the susceptances of more than n branches, which cover all buses, are perturbed. In addition, we analyze the impact of the susceptance perturbations on the attack space. We illustrate our findings on an IEEE test power system using load traces from the state of New York.