I heard a quick blurb on the morning radio news on the drive in to work about this and thought surely the radio announcer got it wrong or "dumbed it down" to the point it didn't make any sense. It went something like this "You can use a laser pointed at your Smart Speaker and control it to open your garage, order pizza, etc)".
Here's the WIRED article:
https://www.wired.com/story/lasers-hack-amazon-echo-google-home/Apparently a high enough power laser source will at some specific frequency cause vibrations to be induced in the membrane of the microphone, creating an electrical signal. Laser-induction of a microphone. What are the physics involved? Is this just air being heated at the surface which expands and then creates a physical push? I can't see how light itself has enough energy to move the membrane. Even the Crookes radiometer works because one side of each vane is black and that side heats the air next to it, allowing it to be pushed. There isn't a perfect vacuum in those devices:
And to defeat the "hack" one could simply cover the microphone with something like a sponge, a 90-degree angled pipe, some angled mirrors or anything that would obstruct a direct-path to the microphone as sound would easily be able to go around the corners or porous material yet inhibit any possibility of a laser hitting the microphone. Or just make the microphone membrane out of a lighter or silvery material, which would reduce air heating (like the back-side of a Crookes radiometer vane). As well, any software update could add something to see if could identify the "signature" of a laser-produced "sound" compared to actual voice. I'm sure after enough analysis it can be distinguished.
MUCH TO DO ABOUT NOTHING!!!!?
?
As always, the media and news radio sensationalize everything!
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