Consumers are increasingly outfitting their homes with smart speakers and displays that use wide-field microphones to pick up voice commands. These devices can be incredibly convenient, but you have to wonder about the privacy implications. That’s not just because the companies hosting your data might do something untoward — it may be possible to exploit these devices to steal data or access connected smart home platforms. Researchers from UEC Tokyo and the University of Michigan have demonstrated one approach to hacking smart speakers using lasers.
Many of today’s smart home devices, smartphones, and tablets use compact and highly sensitive MEMS microphones. Because of the nature of the MEMS components, they respond to light as if it was sound. The researchers found they could direct a laser at smart speakers to take advantage of that, an attack they call Light Command.
Smart speakers like Google Home (Nest), Apple HomePod, and Amazon Echo are constantly listening using local audio processing, but they only “wake up” when someone says the trigger phrase. For example, that’s “Hey Google” or “OK Google” for Google Nest. The key to the attack developed by the international team is that the speakers don’t much care who says the trigger phrase. While some features require voice authentication, most don’t need to make sure you are the account owner to start issuing commands.
In order to trick smart speakers, simply shined a laser directly at the microphone from up to 360 feet (110m) away. From that distance, you need a very powerful laser, but up close, a standard laser pointer has enough power. By modulating the intensity of the light, the team can match the signal of their chosen voice command. You can see the technique working in the above video.
While this is a troubling development for fans of smart home technology, Light Command isn’t going to make all your smart speakers and displays easily hackable. For one, the laser needs to hit the microphone at just the right angle, and the mics are rarely in a convenient location. For example, the Google Home has mics facing up and slightly back. Users will also see the light reflecting off the speaker, and hear the audio feedback when the speaker activates. Still, We wouldn’t be surprised if companies start adding hoods or filters of some sort to make the mics harder to target with lasers.
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