Stephen Downes

Most voice activated home assistants use micro-electro-mechanical systems (MEMS) microphones. These allow speakers to act in reverse, turning sound waves into electrical signals. Unfortunately, however, they also turn light signals into electrical signals. This means you can 'speak' to your voice assistant using pulsed light. And thus, a new way to hack home assistants was born. "By shining the laser through the window at microphones inside smart speakers, tablets, or phones, a far away attacker can remotely send inaudible and potentially invisible commands." See also: Hackaday, Ycombinator, University of Michigan. Also: 17 page PDF.