Voice assistants can be fooled with a laser, and a motion sensor with music

[DronVR]

Voice assistants can be fooled with a laser, and a motion sensor with music

How to hear the light: MEMS microphones and their quirks
It turns out that if you convert a voice command to a laser flicker and direct the beam to the microphone, then the assistant will safely recognize and fulfill the request. This was found by researchers from the University of Electrical Communications of the Japanese city of Tofu and the University of Michigan. They could pass commands to gadgets a distance of several tens of meters. The only condition is that there must be direct line of sight between the source of the laser beam and the microphone of the device.

Researchers tested a laser attack on smart speakers, smartphones, tablets, and other devices running Amazon Alexa, Apple Siri, and Google Assistant. Everywhere the trick worked, only the distance at which the microphone picked up the signal was different - from 5 to 110 meters. Theoretically, the attack range may be longer if the laser power and lens characteristics allow.

In the video below (as an example of what can be done using this method), researchers, sitting in the next building, make the Google Home smart column open the garage.

Why MEMS microphones respond to light
Now a little about how it works. Laser attack is possible due to the features of the device microphones in gadgets. Most modern microphones built into smart electronics relate to microelectromechanical systems (for short - MEMS or MEMS). These are miniature devices in which electronic and mechanical components are combined into one intricate design.

MEMS devices are mass-produced using the same technologies as computer chips, mainly from the same material - silicon, and with the same degree of miniaturization: the dimensions of individual parts of these devices are measured in micrometers or even nanometers. At the same time, MEMS devices are incredibly cheap, so they have already managed to supplant most other design options for sensors and other miniature devices that work at the junction of electronics and the physical world.

The main sensitive part of the MEMS microphone is the thinnest membrane, about a hundred times thinner than a human hair. This membrane oscillates under the influence of sound waves. As a result, the space between it and the fixed part of the sensor increases or decreases. In this case, the membrane and the stationary base of the sensor together form a capacitor, so that when the distance between them changes, the capacitance changes. These changes are easy to measure and record, and then convert to sound recording.

A ray of light can also create waves that cause vibrations of the sensitive membrane. So-called photoacoustic effect known since the end of the XIX century. Then the Scottish scientist Alexander Graham Bell (yes, the one that patented the phone) invented Photo background - a device that allows you to exchange sound messages using a beam of light at a distance of several hundred meters.

Most often, the photoacoustic effect occurs due to the fact that the light heats up what it hits. When heated, objects expand and become larger, and when they cool, they decrease to their original size. That is, under the influence of a flickering laser beam, they will change in size. You will most likely not notice this, but the MEMS sensor is microscopic and susceptible even to microscopic effects. Therefore, he will feel such vibrations and honestly transform it into a sound recording, which will then be recognized as a voice command.

Movement music: MEMS accelerometer sensitivity to sound
MEMS technology is used not only in microphones, but also in many other sensors. Take, for example, motion sensors - gyroscopes and accelerometers. They are in pacemakers, airbags in cars and many others. They are responsible for the screen rotation in smartphones and tablets, and they too can be deceived in an unusual way.

A couple of years ago, researchers from universities in Michigan and South Carolina conducted an experiment, subjecting accelerometers that normally should respond to movement ... sound.

Why MEMS accelerometers respond to sound
And here it is. The sensor detects that the device is moving by displacing the microscopic load. Sound waves can cause load vibrations, causing the accelerometer to think that it is moving in space. Researchers tested two dozen common models of accelerometers, and three quarters of them were susceptible to sound.

So, as part of the study, scientists forced Fitbit fitness bracelet to take fake steps, and a smartphone to steer a radio-controlled machine lying on the table. Typically, a toy responds to the tilt of the gadget, but the researchers tricked the smartphone’s sensor with the music they turned on.

Breathed in with helium: iPhone is off
Not all MEMS quirks are found in the laboratory. The system administrators of one of the American clinics faced a strange phenomenon during the installation of a new MRI device: employees of the medical center started complaining about idle phones . The investigation showed that only Apple devices failed, while gadgets from other manufacturers (as well as computers and medical devices) worked as if nothing had happened.

The culprit of the incident was liquefied helium, which is used to cool the working components of the tomograph. When installing the device, part of the helium leaked, evaporated and spread throughout the clinic - and even a low gas concentration was enough to make iPhones begin to fall into a lethargic dream.

Why do iPhone stop working due to helium
Unlike other equipment in the clinic, in which microelectromechanical devices are also used, but are not critical for the system, in Apple Watch and iPhones, starting from the sixth, they are responsible for the work of the clock generator - in fact, the clock used by all the more intelligent electronics. And without the exact time, devices cannot live.

Inside the MEMS generators, which were the culprits of the failure of iPhones, a vacuum is created necessary for their normal operation. To prevent this vacuum from filling, the chips tightly “seal” with a thin layer of silicon during production. However, helium molecules are so small that they penetrate the silicon crystal lattice and interfere with the normal operation of the microscopic resonator inside the chip. As a result, the electronics go crazy, the iPhone turns off and stops responding to anything.

The fact that Apple gadgets do not tolerate helium, the company knows and even warns in user manual “If the iPhone is in a high concentration of industrial chemicals, including near vaporized liquefied gases, such as helium, the iPhone may be damaged or malfunction.” However, such situations are so rare that few people think about them.

However, having "breathed", the majority of the affected devices returned to normal (although this takes quite a lot of time - up to several days). And the manufacturer of MEMS sensors, which are used in the iPhone, assures that newer generations of devices are immune to such gases.

Take care of your devices
So far, sensor incidents are the exception rather than the rule. Moreover, manufacturers are constantly improving their products, and researchers offer options for protection against simulated attacks. But just in case, we recommend that you keep your gadgets away from windows, helium cylinders and other chemicals.

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