While electromagnetic emissions are present in keyboards, printers, and other electronic devices, the most notable use of Van Eck phreaking is in reproducing the contents of a cathode-ray tube (CRT) display at a distance.
While the phenomenon had been known by the United States Government and Bell Labs as early as the Second World War, the process received its name after Wim van Eck published the first unclassified technical analysis of the security risks of emanations from computer monitors in 1985.
[2][3] This paper caused some consternation in the security community, which had previously believed that such monitoring was a highly sophisticated attack available only to governments; van Eck successfully eavesdropped on a real system, at a range of hundreds of metres, using just $15 worth of equipment plus a television set.
[3] In January 2015, the Airhopper project from Georgia Institute of Technology, United States demonstrated (at 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, to a program running on an Android cellphone with an earbud radio antenna.
This caused the Dutch government to ban the use of NewVote computer voting machines manufactured by SDU in the 2006 national elections, under the belief that ballot information might not be kept secret.
[15] With CRT displays and analog video cables, filtering out high-frequency components from fonts before rendering them on a computer screen will attenuate the energy at which text characters are broadcast.
With modern flat panel displays, the high-speed digital serial interface (DVI) cables from the graphics controller are a main source of compromising emanations.
Adding random noise to the least significant bits of pixel values may render the emanations from flat-panel displays unintelligible to eavesdroppers but is not a secure method.