A team belonging to the University of Michigan has applied laser lights to utilize a wide range of voice-activated devices, which has given them access to everything right from thermostats to garage door openers to front door locks. The researchers have revealed their findings to Amazon, Google, and Apple, who are analyzing the research. Collaborating with researchers of the University of Electro-Communications in Japan, U-M’s researchers published a paper and a website with details of its workings. The team discovered that the microphones in the smart equipment responded to light as if it were sound. Each microphone consists of a small plate called a diaphragm that moves when the sound gets activated. With the help of focused light, like lasers or a focused flashlight, they were able to access the system. This can create security issues, as most of these devices are locked inside houses, light can pass through windows. It can easily travel long distances, restricting the attacker only with regards to their ability to focus and aim the laser beam.
Researchers worked in an almost 120-meter-long hallway and got a voice-activated system to respond. All the equipment that they needed to hack the system was available on Amazon. The attack can be executed using a simple laser pointer, a sound amplifier, and a laser driver, as the researchers described on the website. A telephoto lens can help to focus the laser for long-range attacks. “Microphones convert sound into electrical signals,” the research says. “The main discovery behind light commands is that in addition to sound, microphones also react to light aimed directly at them. Thus, by modulating an electrical signal in the intensity of a light beam, attackers can trick microphones into generating electrical signals as if they are receiving genuine audio.” In other words, the microphone responds to the intensity of laser light the same way it responds to variations in pressure from sound waves. With this mechanism, a hacker can record their voice by issuing a command, use a laser modulator to change it into laser pulses, and transmit it into a piece of equipment, which then operates just like someone was talking to it.
The most obvious way is to ensure your voice-activated devices are not in sight of a window. The devices can also be placed behind an object, such as a bookcase, TV, or picture, because while light waves do not, sound waves can easily go around objects, indicating that the device would still respond to a voice, said Benjamin Cyr, a researcher at U-M.
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