Malicious Reconfigurable Intelligent Surfaces: How Impactful can Destructive Beamforming be?

TL;DR

This paper investigates how malicious reconfigurable intelligent surfaces can intentionally degrade communication quality in multi-user systems, proposing optimal and robust phase-shift strategies under perfect and uncertain channel conditions.

Contribution

It introduces a novel analysis of malicious RIS attacks, deriving optimal phase-shift patterns and robust strategies considering CSI uncertainties, highlighting their impact on system performance.

Findings

Performance degradation scales with the number of RIS elements.

Robust optimization effectively mitigates CSI uncertainties.

Malicious RIS can significantly impair specific user signals.

Abstract

Reconfigurable intelligent surfaces (RISs) have demonstrated significant potential for enhancing communication system performance if properly configured. However, a RIS might also pose a risk to the network security. In this letter, we explore the impact of a malicious RIS on a multi-user multiple-input single-output (MISO) system when the system is unaware of the RIS's malicious intentions. The objective of the malicious RIS is to degrade the \ac{SNR} of a specific \ac{UE}, with the option of preserving the SNR of the other UEs, making the attack harder to detect. To achieve this goal, we derive the optimal RIS phase-shift pattern, assuming perfect channel state information (CSI) at the hacker. We then relax this assumption by introducing CSI uncertainties and subsequently determine the RIS's phase-shift pattern using a robust optimization approach. Our simulations reveal a direct proportionality between the performance degradation caused by the malicious RIS and the number of reflective elements, along with resilience toward CSI uncertainties.