As you can understand from the name, the attack relies on the use of built-in lidar, which is used to navigate in space. In fact, a potential attacker can use lidar and its laser as a laser microphone. Laser microphones are often used by special services, especially if the recording needs to be made from a distance. For example, a laser microphone is pointed at a window glass and uses it to track glass vibrations, which can then be decoded and decrypted for conversations that took place inside the room.
Experts note that the LidarPhone attack requires compliance with certain conditions. For example, the attacker will be forced to use some small device or intervene in the process of updating the device so as to gain control over the lidar. The fact that the device lidar is active and spinning all the time, which reduces the amount of data that an attacker can collect. With malicious firmware, the attacker can stop the rotation and normal operation of the lidar, forcing it to focus on a single object, tracking the surface vibration due to sound waves.
It should also be noted that the lidars of robotic vacuum cleaners are far from as accurate as laser microphones, so the collected readings, which will be transmitted to the remote server of the attacker, will have to be further processed by amplifying the signal so that the received sound can be parsed by a person.
Despite all these limitations, the researchers managed to get good results during the tests on the Xiaomi Roborock vacuum cleaner. The experts performed a number of tests using lidar to remove the signal from different objects, and during the tests there was a different distance between the vacuum cleaner and the sound source.
At the same time, the researchers’ experiments were mainly focused on restoring numerical values rather than conversations, which were eventually restored with an accuracy of 90%. However, the authors of the attack note that the LidarPhone can be used to identify sex speakers and even to determine political views on the targets of news items sounding in the background.
Although LidarPhone is more of a theoretical attack, for protection, the researchers recommend the manufacturers of robotic vacuum cleaners to disable lidar devices when it is not used.
The researchers’ report was presented at the ACM Conference on Embedded Networked Sensor Systems (SenSys 2020). The recording of the research group’s presentation can be seen below.