Researchers from China’s Zhejiang University have discovered a clever way of activating your voice recognition systems without speaking a word. The attack technique works by feeding the AI assistants commands in ultrasonic frequencies, which are too high for humans to hear but are perfectly audible to the microphones on your smart devices. With this technique, cyber criminals can “silently” whisper commands into your smartphones to hijack Siri and Alexa, and could force them to open malicious websites and even your door if you have a smart lock connected.
Source: https://thehackernews.com/2017/09/ai-digital-voice-assistants.html