Code of "Sirens' Whisper: Inaudible Near-Ultrasonic Jailbreaks of Speech-Driven LLMs"

## Introduction Large language models (LLMs) are increasingly deployed in voice interfaces such as smartphones, smart speakers, and in-vehicle systems, which broadens the attack surface to the acoustic front end. **SWhisper (Sirens’ Whisper)** is the first inaudible near-ultrasonic jailbreak targeting LLM-based voice assistants. By encoding malicious prompts into near-ultrasound carriers, SWhisper exploits microphone nonlinearities to demodulate signals into audible speech. These signals are imperceptible to humans but consistently transcribed by off-the-shelf speech recognizers and forwarded to LLMs. Key aspects include: - Decoupling audio from semantics: prompts are semantically fluent, short, and…

• NS
  National Science Foundation

  Award: 1943016
• DA
  Defense Advanced Research Projects Agency

  Awards: FA8750, FA8750-15-2-0277
• MU
  Multidisciplinary University Research Initiative
• AR
  Army Research Office

  Awards: W911NF-21-1-, W911NF