Grounds for Suspicion: Physics-based Early Warnings for Stealthy Attacks on Industrial Control Systems

TL;DR

This paper introduces a physics-based framework for providing early warnings of stealthy attacks on industrial control systems by assessing attack feasibility and proximity to unsafe states, validated on a chemical process case study.

Contribution

It proposes a novel suspicion metric based on physical process behavior, formulated as a real-time reachability problem, to give early warnings before damage occurs.

Findings

Early warnings can be issued before physical damage occurs.

The suspicion metric is effective in real-time detection.

Framework validated on Tennessee-Eastman process case study.

Abstract

Stealthy attacks on Industrial Control Systems can cause significant damage while evading detection. In this paper, instead of focusing on the detection of stealthy attacks, we aim to provide early warnings to operators, in order to avoid physical damage and preserve in advance data that may serve as an evidence during an investigation. We propose a framework to provide grounds for suspicion, i.e. preliminary indicators reflecting the likelihood of success of a stealthy attack. We propose two grounds for suspicion based on the behaviour of the physical process: (i) feasibility of a stealthy attack, and (ii) proximity to unsafe operating regions. We propose a metric to measure grounds for suspicion in real-time and provide soundness principles to ensure that such a metric is consistent with the grounds for suspicion. We apply our framework to Linear Time-Invariant (LTI) systems and formulate the suspicion metric computation as a real-time reachability problem. We validate our framework on a case study involving the benchmark Tennessee-Eastman process. We show through numerical simulation that we can provide early warnings well before a potential stealthy attack can cause damage, while incurring minimal load on the network. Finally, we apply our framework on a use case to illustrate its usefulness in supporting early evidence collection.