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. Van Eck phreaking might also be used to compromise the secrecy of the votes in an election using electronic voting. 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.In a 2009 test of electronic voting systems in Brazil, Van Eck phreaking was used to successfully compromise ballot secrecy as a proof of concept.
Eavesdropping Through a Wall From The New Scientist:
With half a century's experience of listening to feeble radio signals from space, NASA is helping US security services squeeze super-weak bugging data from Earth-bound buildings.
It is easy to defeat ordinary audio eavesdropping, just by sound-proofing a room. And simply drawing the curtains can defeat newer systems, which shine a laser beam onto a glass window and decode any modulation of the reflected beam caused by sound vibrations in the room.
So the new "through-the-wall audio surveillance system" uses a powerful beam of very high frequency radio waves instead of light. Radio can penetrate walls – if they didn't, portable radios wouldn't work inside a house.
The system uses a horn antenna to radiate a beam of microwave energy –between 30 and 100 gigahertz – through a building wall. If people are speaking inside the room, any flimsy surface, such as clothing, will be vibrating. This modulates the radio beam reflected from the surface.
Although the radio reflection that passes back through the wall is extremely faint, the kind of electronic extraction and signal cleaning tricks used by NASA to decode signals in space can be used to extract speech.
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I dont personally know anything about the Brazilian incident. The information otherwise is accurate. Those of you at home can get an idea of what is being discussed if you still have access to a crt. Just set a radio next to the crt. Start at the bottom station and slowly dial up. At some point the EMI from the radio matches the frequency of the crt and disrupts the picture. This is vaguely similar to the more advanced techniques being discussed.
Realize then of course that if the radio is sending signals to the crt then other electronics are sending signals to the radio. The radio is plugged into the wall and as far as the signal is concerned a wire is a wire regardless of what we intended for that wire.
Some of our older Freeps will remember things like mom using the vacuum disrupting the television or the mixer being heard on the radio instead of their song.
You can also eavesdrop on conversations by extracting them from the vibrations of nearby objects. This has been demonstrated using a potato chip bag. The eavesdropper needs hi resolution video of the object (bag) and then measures its movement caused by the sound waves of the speaker.