Analysis of Security Indices in Hybrid Cyber Attacks of Power Network State Estimation

Security indices has been introduced to analyze the vulnerability of sensors in steady-state power networks. A security index for some sensor is defined by the minimum number of sensors that must simultaneously attack to realize a stealthy cyber attack called a False Data Injection (FDI) attack. In this paper, we analyze the change of security indices occurred by a hybrid cyber attack that combines an FDI attack and a Denial-of-Service (DoS) attack. We theoretically show that security indices are decreased at most one by a hybrid cyber attack. Furthermore, under a hybrid cyber attack, we also discuss the relation between security indices and the sensor scheduling-based attack detection method.