A Moving Target Defense to Detect Stealthy Attacks in Cyber-Physical Systems

Abstract

Cyber-Physical Systems (CPS) have traditionally been considered more static, with regular communication patterns when compared to classical information technology networks. Because the structure of most CPS remains unchanged during long periods of time, they become vulnerable to adversaries who can tailor their attacks based on their precise knowledge of the system dynamics, communications, and control. Moving Target Defense (MTD) has emerged as a strategy to add uncertainty about the state and execution of a system in order to prevent adversaries from having predictable effects with their attacks. In this work we propose a novel type of MTD strategy that randomly changes the availability of the sensor data, so that it is harder for adversaries to tailor stealthy attacks and at the same time it can minimize the impact of false-data injection attacks. Using tools from switched control systems we formulate an optimization problem to find the probability of the switching signals that increase the visibility of stealthy attacks while decreasing the deviation caused by false data injection attacks.

Resilience Estimation of Cyber-Physical Systems via Quantitative Metrics

“…The dynamics is concealed to the adversary. Because it is time-varying, it becomes a moving target that is challenging to identify by an adversary, a precondition to the covert attack [7]. But, it is known to and used by the operator to detect the covert attack.…”

Switched-Based Resilient Control of Cyber-Physical Systems

“…III.3 CPS-based MTD approaches -Most CPS-based MTD approaches have been proposed to control adversaries situated in the end devices, i.e., actuators and sensors. For example, in [11], authors propose a MTD strategy that randomly changes the availability of the sensor data, so that it is harder for adversaries to achieve stealthy attacks. This approach uses switched control systems that allow to detect sensor compromise and to minimize the impact of falsedata injection attacks.…”

“…As showed in recent surveys [7] [8] [9], most of the existing approaches require adding extra hardware [10], which may be expensive. Other solutions use detection approaches with recovery strategies [11] [12] [13] [14] that usually use state estimation to maintain an understanding of the system state under attack, even when a subset of inputs and outputs are compromised. These techniques work as traditional detection and mitigation approaches but do not provide resilience-by-design or prevent the execution of malicious commands.…”

A Nash equilibrium-based moving target defense against stealthy sensor attacks

“…An emerging approach to detect attacks and to limit their impact, which can combine both physical models and game theory, are moving target defense (MTD) strategies [6] that induce controlled uncertainties into the CPS to confuse the attacker. Gairo et al [7], for example, randomly switch between the sensors used to detect otherwise stealthy attacks, while in [8] a random watermarking signal is injected into the CPS to make stealthy attacks detectable. However, the MTD strategies in [7] and [8] directly influence the closed-loop behavior of the CPS and can decrease its performance.…”

“…Gairo et al [7], for example, randomly switch between the sensors used to detect otherwise stealthy attacks, while in [8] a random watermarking signal is injected into the CPS to make stealthy attacks detectable. However, the MTD strategies in [7] and [8] directly influence the closed-loop behavior of the CPS and can decrease its performance. Griffioen et al [9] propose a MTD scheme that introduces an auxiliary system to not influence the closed-loop behavior and simultaneously detect an attack.…”