The CIA, NSA and HAM or amateur radio enthusiast have been doing this for years with computers and passing around programs for decoding the computer/electronic device "noise" picked up by AM radios.
Back in the 70's some computer programmers/engineers used to use what I think was an old PDP series computer with a AM radio set near a cable as a form of Audio output and were able to play simple tunes on the radio or tell what type of programs were running and what pats the programs were using in the computer.. Morse code was a way to get information out to the user without using the printers.
I've been hearing rumours/stories for years that the NSA, CIA and FBI along with the many 3 letter organizations of at least half the world having "virus code" to increase the bandwidth and transmission range of this Side channel information/(noise) broadcast when a computer operates, especially when it prints, displays something on a monitor or in general send signals along wires to other devices.(It's not limited to EM noise, sound and light are also useful side channels.)
TEMPEST is a code name for a standard that attempts to reduce or limit side channel transmissions. I run across this code name better than 30 years ago when I was trying to find better ways of silencing the electronic interference induced into my radios and to reduce my radios interfering with the mostly unshielded consumer electronics.
http://en.wikipedia.org/wiki/TEMPEST
Lately their has been a big breakthrough in the cost of software defined radios in the form of a $15 to $35 USB TVdongle that can tune from around 20 megahertz to say roughly 2 Gigahertz.
http://www.amazon.com/NooElec-NESDR-Mi ... MFZXNEFB67
or
http://www.amazon.com/DVB-T-RTL2832U-R ... ined+radio
The above are at the two extremes one has been specifically modified to operate better as a software defined radio and HAM, Electrical Engineers and security tasked with meeting the TEMPEST standard or just trying to cut interference love these little dongles. You can plug them into a shielded laptop or tablet or even a more expensive phone and you have a wide band near star trek level "tricorder" sensor able to be carried in your hands a brief case or even a larger pocket and can store analyze/ decode any signal that has less than roughly 4 Megahertz bandwidth.
I've seen discussion dealing with using these dongles to create passive simplistic RADARS from the environments transmitted noise signals. You can use these dongles right now with open source software to track every FAA approve aircraft that is in line of sight.(The FAA and most other nations require most passenger aircraft to have a beacon that is tied to GPS that constantly broadcast their positions.)
Nearly all the software for these dongles is open source and easily interfaces with custom or public domain signal decoders. Since the information is being recorded you could even write your own custom programs in say BASIC to decode the signals later.
HM
Edited to fix link
Back in the 70's some computer programmers/engineers used to use what I think was an old PDP series computer with a AM radio set near a cable as a form of Audio output and were able to play simple tunes on the radio or tell what type of programs were running and what pats the programs were using in the computer.. Morse code was a way to get information out to the user without using the printers.
I've been hearing rumours/stories for years that the NSA, CIA and FBI along with the many 3 letter organizations of at least half the world having "virus code" to increase the bandwidth and transmission range of this Side channel information/(noise) broadcast when a computer operates, especially when it prints, displays something on a monitor or in general send signals along wires to other devices.(It's not limited to EM noise, sound and light are also useful side channels.)
TEMPEST is a code name for a standard that attempts to reduce or limit side channel transmissions. I run across this code name better than 30 years ago when I was trying to find better ways of silencing the electronic interference induced into my radios and to reduce my radios interfering with the mostly unshielded consumer electronics.
http://en.wikipedia.org/wiki/TEMPEST
Lately their has been a big breakthrough in the cost of software defined radios in the form of a $15 to $35 USB TVdongle that can tune from around 20 megahertz to say roughly 2 Gigahertz.
http://www.amazon.com/NooElec-NESDR-Mi ... MFZXNEFB67
or
http://www.amazon.com/DVB-T-RTL2832U-R ... ined+radio
The above are at the two extremes one has been specifically modified to operate better as a software defined radio and HAM, Electrical Engineers and security tasked with meeting the TEMPEST standard or just trying to cut interference love these little dongles. You can plug them into a shielded laptop or tablet or even a more expensive phone and you have a wide band near star trek level "tricorder" sensor able to be carried in your hands a brief case or even a larger pocket and can store analyze/ decode any signal that has less than roughly 4 Megahertz bandwidth.
I've seen discussion dealing with using these dongles to create passive simplistic RADARS from the environments transmitted noise signals. You can use these dongles right now with open source software to track every FAA approve aircraft that is in line of sight.(The FAA and most other nations require most passenger aircraft to have a beacon that is tied to GPS that constantly broadcast their positions.)
Nearly all the software for these dongles is open source and easily interfaces with custom or public domain signal decoders. Since the information is being recorded you could even write your own custom programs in say BASIC to decode the signals later.
HM
Edited to fix link