Risk assessment of coordinated cyber-physical attacks against power grids: A stochastic game approach

In this paper, the risk assessment of coordinated cyber-physical attacks against power grids is investigated using a novel game-theoretic framework. In particular, to address the dynamic nature of the power grid protection, a stochastic budget allocation game is proposed to analyze the strategic interactions between a malicious attacker and the grid defender while factoring in the attack and defense budget limitations. In this game, the attacker intends to maximize the physical impacts of coordinated attacks on the grid while the defender aims to minimize these impacts. An optimal load shedding problem is formulated to measure such physical impacts under successful attacks, and these impacts are then incorporated into a learning algorithm as inputs for finding the Nash equilibrium of the game. The two players' optimal strategies at Nash equilibrium, in terms of attacking/protecting the critical grid elements, can be used to assess the risk faced by the grid at various states. In addition, the optimal defense budget allocation strategy is expressed in terms of the corresponding risk. The proposed stochastic game framework is tested on the IEEE 9-bus system for illustrative purpose, and risk sensitivity to the attack/defense budget variation is analyzed.