Enhancing Cybersecurity in Industrial Control System with Autonomous Defense Using Normalized Proximal Policy Optimization Model.

Industrial control networks are frequent targets of cyber attacks, calling for autonomous defense strategies to combat threats effectively and promptly. We propose to leverage Reinforcement Learning (RL) to train defenders how to select the most appropriate actions in response to attackers’ behavior. We model the defender and attacker as agents in RL environments and define action space and reward function. We focus on evaluating value-based and policy gradient-based RL algorithms and propose enhancements to Proximal Policy Optimization (PPO) method through normalization. We then leverage CybORG, a simulation tool to study how the RL algorithms perform to achieve autonomous defense. Our extensive experiments reveal that the proposed normalized PPO outperforms other models in terms of stability, robustness, and average rewards. The results also demonstrate the effectiveness of the defender in protecting the operational server upon changing the attacker’s position. Additionally, increasing the number of attackers had a significant impact on policy-based algorithms, particularly PPO, with decreased reward values highlighting the increased vulnerability of the network.