MAARS: Multi-Rate Attack-Aware Randomized Scheduling for Securing Real-time Systems

In modern Cyber-Physical Systems (CPSs), most of the safety-critical tasks are executed with a fixed sampling period to ensure deterministic timing behaviour. However, adversaries can exploit this deterministic behaviour of periodic safety-critical tasks to launch schedule-based attacks (SBAs) on them. This paper aims to prevent and minimize the possibility of SBAs by switching between strategically chosen periodicities of control tasks while ensuring that their performance remains unhampered. Thereafter, we present a novel schedule vulnerability analysis methodology to switch between valid task schedules generated at run time. Overall, we introduce a novel Multi-Rate Attack-Aware Randomized Scheduling (MAARS) framework for preemptive fixed-priority schedulers that minimize the success rate of timing-inference-based attacks on safety-critical real-time systems. We evaluate the efficacy of MAARS in terms of attack prevention on synthetic task sets and an automotive benchmark task set in a Hardware-in-the-Loop (HIL) environment.