  In this study, we investigate the emerging threat of inaudible acoustic
attacks targeting digital voice assistants, a critical concern given their
projected prevalence to exceed the global population by 2024. Our research
extends the feasibility of these attacks across various platforms like Amazon's
Alexa, Android, iOS, and Cortana, revealing significant vulnerabilities in
smart devices. The twelve attack vectors identified include successful
manipulation of smart home devices and automotive systems, potential breaches
in military communication, and challenges in critical infrastructure security.
We quantitatively show that attack success rates hover around 60%, with the
ability to activate devices remotely from over 100 feet away. Additionally,
these attacks threaten critical infrastructure, emphasizing the need for
multifaceted defensive strategies combining acoustic shielding, advanced signal
processing, machine learning, and robust user authentication to mitigate these
risks.
