Researchers from David Ben-Gurion University (Israel), the study of hidden methods of transmitting data from isolated computers, a new method of organizing a communication channel based on signal modulation through a change in the brightness of the LCD screen that is imperceptible to the eye. From a practical point of view, the method can be used, for example, to transfer encryption keys, passwords and secret data from a computer without a network connection that is infected with spyware or malware.
For coding "1", an increase in the brightness of the red component of the color of the pixels by 3% relative to the nominal value is used, and "0" - a decrease in brightness by 3%. Changes in brightness that occur during data transmission are imperceptible to humans, and the method can also be used while the operator is working at the computer from which data is being extracted. The information modulated by changing the brightness can be extracted from video recordings, including those taken by CCTV cameras, web cameras and smartphones.
The transmission speed is only a few bits per second. For example, when using a Sony SNC-DH120 720P video surveillance camera and a Microsoft Lifecam webcam, we were able to receive data from a distance of up to 9 meters at a speed of 5-10 bits per second. When using the camera of the Samsung Galaxy S7 smartphone, the signal reception distance was reduced to one and a half meters, and the transmission rate dropped to 1 bit per second.
On the also formed a selection of other methods of covert data transmission studied by researchers using electromagnetic, acoustic, thermal and light forms of leaks:
- — sending data over the power line, manipulating the load on the CPU to change the power consumption;
- () - data outside the audible range through passive speakers or headphones without using a microphone;
- () — demonstration of data extraction from a device located in a shielded room (Faraday cage) through the analysis of low-frequency magnetic oscillations that occur during CPU operation;
- () - data extraction based on the measurement of magnetic field fluctuations that occur during CPU operation;
- () - data transfer at a speed of up to 60 bytes per second from a PC to a smartphone through analysis on a smartphone with an FM tuner of radio interference that occurs when information is displayed on the display;
- () - data transmission at a distance of up to 40 cm at a speed of 1-8 bits per hour through the measurement of temperature fluctuations in the PC case;
- () - extracting data at a distance of up to 30 meters through the creation of electromagnetic interference at the frequency of GSM networks captured by a smartphone;
- () - data transfer at a speed of 180 bits per minute through the analysis of sounds emitted during manipulations with the hard disk;
- () - data transfer at a speed of up to 80 bytes per second through the analysis of electromagnetic interference generated in the process of accessing devices via the USB port;
- () - the use of an LED with an indication of hard disk activity as a data transfer source at a speed of up to 120 bits per second when using a conventional video camera as a receiver and up to 4000 bits per second when using a special sensor;
- () - data transfer at a speed of up to 900 bits per hour through the modulation of the change in the sound of the cooler used to cool the CPU;
- () - data transmission through the infrared LED of surveillance cameras at a speed of 100 bits per second and at a distance of up to a kilometer;
- () - data transfer at speeds up to 10 thousand bits per second through flashing LEDs on hacked routers and switches;
- - data transmission through invisible flickering or changes in the contrast of the image on the screen.
Source: opennet.ru