SUAD: Solid-Channel Ultrasound Injection Attack and Defense to Voice Assistants

TL;DR

This paper introduces SUAD, a novel long-range, cross-barrier inaudible attack on voice assistants via solid channels, and a universal ultrasonic perturbation defense that effectively blocks such attacks without affecting normal speech.

Contribution

It presents the first solid-channel inaudible attack method and a universal ultrasonic defense mechanism for voice assistants, enhancing security against long-range and cross-barrier threats.

Findings

SUAD Attack achieves over 89.8% success rate in activating voice assistants.

SUAD Defense blocks inaudible voice attacks with over 98% success rate.

The methods are effective across six different smartphones.

Abstract

As a versatile AI application, voice assistants (VAs) have become increasingly popular, but are vulnerable to security threats. Attackers have proposed various inaudible attacks, but are limited by cost, distance, or LoS. Therefore, we propose \name~Attack, a long-range, cross-barrier, and interference-free inaudible voice attack via solid channels. We begin by thoroughly analyzing the dispersion effect in solid channels, revealing its unique impact on signal propagation. To avoid distortions in voice commands, we design a modular command generation model that parameterizes attack distance, victim audio, and medium dispersion features to adapt to variations in the solid-channel state. Additionally, we propose SUAD Defense, a universal defense that uses ultrasonic perturbation signals to block inaudible voice attacks (IVAs) without impacting normal speech. Since the attack can occur at arbitrary frequencies and times, we propose a training method that randomizes both time and frequency to generate perturbation signals that break ultrasonic commands. Notably, the perturbation signal is modulated to an inaudible frequency without affecting the functionality of voice commands for VAs. Experiments on six smartphones have shown that SUAD Attack achieves activation success rates above 89.8% and SUAD Defense blocks IVAs with success rates exceeding 98%.