We present METAATTACK, the first approach to leverage acoustic metamaterials for inaudible attacks for voice control systems. Compared to the state-of-the-art inaudible attacks requiring complex and large speaker setups, METAATTACK achieves a longer attacking range and higher accuracy using a compact, portable device small enough to be put into a carry bag. These improvements in portability and stealth have led to the practical applicability of inaudible attacks and their adaptation to a wider range of scenarios. We demonstrate how the recent advancement in metamaterials can be utilized to design a voice attack system with carefully selected implementation parameters and commercial off-the-shelf components. We showcase that METAATTACK can be used to launch inaudible attacks for representative voice-controlled personal assistants, including Siri, Alexa, Google Assistant, XiaoAI, and Xiaoyi. The average word accuracy of all assistants is 76%, with a range of 8.85 m.

翻译：本文提出METAATTACK，这是首个利用声学超材料实现语音控制系统无声攻击的方法。与现有需要复杂大型扬声器装置的无声攻击技术相比，METAATTACK通过可放入随身包的紧凑便携设备，实现了更长的攻击距离和更高的准确率。这些在便携性与隐蔽性方面的改进，使得无声攻击具有实际应用价值，并能适应更广泛的场景。我们展示了如何利用超材料领域的最新进展，通过精心选择的实现参数和商用现成组件来设计语音攻击系统。实验证明，METAATTACK可对包括Siri、Alexa、Google Assistant、小爱同学和小艺在内的代表性语音助手发起无声攻击。所有助手的平均词语识别准确率达76%，有效攻击距离为8.85米。