MetaGuardian: Enhancing Voice Assistant Security through Advanced Acoustic Metamaterial

Abstract

We present MetaGuardian, a voice assistant (VA) protection system based on acoustic metamaterials. MetaGuardian can be directly integrated into the enclosures of various smart devices, effectively defending against inaudible, adversarial and laser attacks without relying on additional soft- ware support or altering the underlying hardware, ensuring usability. To achieve this, MetaGuardian leverages the mutual impedance effects between metamaterial units to extend the signal filtering range to 16-40 kHz to effectively block wide-band inaudible attacks. Additionally, it adopts a care- fully designed coiled space structure to precisely interfere with adversarial attacks while ensuring the normal functioning of VAs. Furthermore, MetaGuardian offers a universal structural design, allowing itself to be flexibly adapted to various smart devices, striking a balance between portability and protection effectiveness. Empirical evaluations indicate that MetaGuardian attains a 100% defense success rate against five recognized adversarial attacks, three inaudible attacks, and one laser attack observed in recent years at common attack ranges.