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A team of cybersecurity researchers has discovered a clever technique to remotely inject inaudible and invisible commands into voice-controlled devices — all just by shining a laser at the targeted device instead of using spoken words.

Dubbed ‘Light Commands,’ the hack relies on a vulnerability in MEMS microphones embedded in widely-used popular voice-controllable systems that unintentionally respond to light as if it were sound.

According to experiments done by a team of researchers from Japanese and Michigan Universities, a remote attacker standing at a distance of several meters away from a device can covertly trigger the attack by simply modulating the amplitude of laser light to produce an acoustic pressure wave.

“By modulating an electrical signal in the intensity of a light beam, attackers can trick microphones into producing electrical signals as if they are receiving genuine audio,” the researchers said in their paper [PDF].

Doesn’t this sound creepy? Now read this part carefully…

Smart voice assistants in your phones, tablets, and other smart devices, such as Google Home and Nest Cam IQ, Amazon Alexa and Echo, Facebook Portal, Apple Siri devices, are all vulnerable to this new light-based signal injection attack.

“As such, any system that uses MEMS microphones and acts on this data without additional user confirmation might be vulnerable,” the researchers said.

Since the technique ultimately allows attackers to inject commands as a legitimate user, the impact of such an attack can be evaluated based on the level of access your voice assistants have over other connected devices or services.

Therefore, with the light commands attack, the attackers can also hijack any digital smart systems attached to the targeted voice-controlled assistants, for example:

  • Control smart home switches,
  • Open smart garage doors,
  • Make online purchases,
  • Remotely unlock and start certain vehicles,
  • Open smart locks by stealthily brute-forcing the user’s PIN number.

As shown in the video demonstration listed below: In one of their experiments, researchers simply injected “OK Google, open the garage door” command to a Google Home by shooting a laser beam at Google Home that was connected to it and successfully opened a garage door.​

images from Hacker News