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

Computer Science > Cryptography and Security [Submitted on 4 Aug 2025 (v1), last revised 25 Mar 2026 (this version, v2)] SUAD: Solid-Channel Ultrasound Injection Attack and Defense to Voice Assistants Chao Liu, Zhezheng Zhu, Hao Chen, Kaiwen Guo, Penghao Wang, Xiang-Yang Li 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%. Subjects: Cryptography and Security (cs.CR) Cite as: arXiv:2508.02116 [cs.CR]   (or arXiv:2508.02116v2 [cs.CR] for this version)   https://doi.org/10.48550/arXiv.2508.02116 Focus to learn more Submission history From: Hao Chen [view email] [v1] Mon, 4 Aug 2025 06:51:36 UTC (6,212 KB) [v2] Wed, 25 Mar 2026 11:56:55 UTC (9,062 KB) Access Paper: HTML (experimental) view license Current browse context: cs.CR < prev   |   next > new | recent | 2025-08 Change to browse by: cs References & Citations NASA ADS Google Scholar Semantic Scholar Export BibTeX Citation Bookmark Bibliographic Tools Bibliographic and Citation Tools Bibliographic Explorer Toggle Bibliographic Explorer (What is the Explorer?) Connected Papers Toggle Connected Papers (What is Connected Papers?) Litmaps Toggle Litmaps (What is Litmaps?) scite.ai Toggle scite Smart Citations (What are Smart Citations?) Code, Data, Media Demos Related Papers About arXivLabs Which authors of this paper are endorsers? | Disable MathJax (What is MathJax?)