Van Eck Phreaking- A Hack Using E-Radiations
Van Eck phreaking is a form of eavesdropping in which special equipment is used to pick up side-band electromagnetic emissions from electronics devices that correlate to hidden signals or data for the purpose of recreating these signals or data in order to spy on the electronic device. Side-band electromagnetic radiation emissions are present in, and with the proper equipment, can be captured from keyboards, computer displays, printers, and other electronic devices.
Van Eck phreaking of CRT displays is the process of eavesdropping on the contents of a CRT by detecting its electromagnetic emissions. It is named after Dutch computer researcher Wim van Eck, who in 1985 published the first paper on it, including proof of concept. Phreaking is the process of exploiting telephone networks, used here because of its connection to eavesdropping.
Information that drives the video display takes the form of high frequency electrical signals. These oscillating electric currents create electromagnetic radiation in the RF range. These radio emissions are correlated to the video image being displayed, so, in theory, they can be used to recover the displayed image.
In a CRT the image is generated by an electron beam that sweeps back and forth across the screen. The electron beam excites the phosphor coating on the glass and causes it to glow. The strength of the beam determines the brightness of individual pixels . The electric signal which drives the electron beam is amplified to hundreds of volts from TTL circuitry. This high frequency, high voltage signal creates electromagnetic radiation that has, according to Van Eck, “a remarkable resemblance to a broadcast TV signal”. The signal leaks out from displays and may be captured by an antenna, and once synchronization pulses are recreated and mixed in, an ordinary analog television receiver can display the result. The synchronization pulses can be recreated either through manual adjustment or by processing the signals emitted by electromagnetic coils as they deflect the CRT’s electron beam back and forth.
In the paper, Van Eck reports that in February 1985 a successful test of this concept was carried out with the cooperation of the BBC. Using a van filled with electronic equipment and equipped with a VHF antenna array, they were able to eavesdrop from a “large distance”.
Van Eck phreaking and protecting a CRT display from it was demonstrated on an episode of Tech TV’s The Screen Savers on December 18, 2003.
In April 2004, academic research revealed that flat panel and laptop displays are also vulnerable to electromagnetic eavesdropping. The required equipment for espionage was constructed in a university lab for less than US$2000.
Communicating using Van Eck phreaking
In January 2015, the Airhopper project from Georgia Institute of Technology, USA demonstrated (at the Ben Gurion University, Israel) the use of Van Eck Phreaking to enable a keylogger to communicate through video signal manipulation keys pressed on the keyboard of a standard PC computer, to a program running on Android cellphone with earbud radio antenna.
Tailored Access Batteries
A tailored Access Battery is a special laptop with Van Eck Phreaking electronics and power-side band encryption cracking electronics built-into the casing of the battery in combination with a remote transmitter/receiver. This allows for quick installation and removal of spying device by simply switching the battery.
Countermeasures are detailed in the article on TEMPEST, the NATO’s standard on spy-proofing digital equipment. One countermeasure involves shielding the equipment to minimize electromagnetic emissions. Another method, specifically for video information, scrambles the signals such that the image is perceptually undisturbed, but the emissions are harder to reverse engineer into images. Examples of this include low pass filtering fonts and randomizing the least significant bit of the video data information.
Another approach is to randomly shift the frequency of the clock used on keyboards with a custom chip containing a pseudorandom number generator (PRNG) with a long length and use an identical synchronized PRNG at the reception end to confound such attacks.
Eckbox is van Eck phreaking software. It interprets a radio signal emanating from a computer’s monitor to recreate the image (in black and white) that is displayed on it. This could be used as a valuable security tool for testing otherwise secure computers, or for developing hardware and software to counter this type of remote shoulder-surfing.
author : cialfor
Updated : 9/26/2016