A pair of Japanese researchers have discovered that laser light can be used to send “voice” commands to a wide variety of smart phones and home voice assistants effectively taking control of the device.

Takeshi Sugawara and Kevin Fu told Wired that they stumbled across the fact that a laser light pointed at the mic found on many smart devices was picked up and interpreted by the device as sound. After several more months of effort the duo were able to use a laser to speak to and have the devices respond to commands by varying the laser light’s intensity. Depending up on the device targeted and the power of the laser, the smart products could be silently controlled from hundreds of feet away, the told Wired.

The longest distance the laser light was effective was 361 feet, although it only worked in a few cases. The laser was also able to penetrate a window and control a Google Home from 250 feet away, Wired reported. The laser’s used ranged from 60-milliwatt to 5-milliwatt (the power of a simple laser pointer.)

Sugawara and Fu are still uncertain why the laser is able to effect the microphones.

Device that require a passcode, voice command tuned to the owner or other initial security layer are more secure against a laser, but the Echo, Home and Apple devices that use a simple wake word can easily be taken over, Wired wrote.