EchoAttack: Practical Inaudible Attacks To Smart Earbuds.

Recent years have shown substantial interest in revealing vulnerability issues of voice-controllable systems on smartphones and smart speakers. While significant prior works have leveraged inaudible signals to attack these smart devices, smart earbuds present unique challenges and vulnerabilities due to their extreme hardware constraints. In this paper, we present EchoAttack, a practical inaudible attack system for smart earbuds. The primary innovation of EchoAttack is the ability to leverage both indirect and direct paths to attack smart earbuds. To search for the optimal path, we design a path-searching algorithm based on the attenuation model of ultrasound. We also propose a novel approach to remove harmonics noise, which improves the attacking signal's SNR further. Finally, we propose using Zigbee radios to sniff the Bluetooth signal and enable a hidden feedback channel without the victim's awareness. We implement the EchoAttack prototype using off-the-shelf hardware components and evaluate the prototypes in four typical indoor and outdoor scenarios using six smart earbuds. Experimental results show that EchoAttack outperforms the pure direct-path attack by 75.8% on average in terms of attack success rate.