Electro magnetic radiation leakage?

Question

How do you build a device that picks up The enormous electromagnetic field generated by a mobile phone or computer monitor and interprets the signal into audio or video (for spying purposes). I know it is possible in theory

Answer 1

Take a cheap transistor radio and take the back off and remove the variable capacitor. That's the bit with the knob on that tunes it. Now it will pick up all frequencies. it won't tune to one. Take it near a bug ( a transmitter) in a room and it will pick that up and the strong signal will be stronger than all the rest it's picking up.Picking it up is easy. Interpreting signals - especially from computers is a little harder..... you need a computer and special software. Ask at GCHQ... LOL

Answer 2

The device you need is simply an antenna. In most cases, the antennas used for spying purposes are very directional. That is, they collect energy from a very narrow band, so they need to be aimed very tightly at, for example, the analog video cable connecting a computer to its monitor or a network cable carrying information among a group of computers. Their directionality is needed to collect as much energy from the source of interest while blocking out surrounding noise.

As things become digital, it becomes more difficult to pick up and interpret information in this manner. The digital information can be encrypted very easily, and even if it isn't, it is much more difficult to decode than an analog representation of the information. Additionally, digital information is usually transmitted with less power, which makes it more difficult to detect it.

These devices are regularly employed by signal information agencies, like the CIA. In fact, the CIA building is surrounded by two panes of glass that include a high density gas as well as white (uncorrelated) acoustic noise piped in between them. This is to prevent a similar type of acoustic eaves dropping -- a laser can be aimed at a window and the reflection can be used to construct an analog to the acoustic vibrations within the remote room.

Other intelligence agency buildings are surrounded by copper shielding (that is usually grounded, but that's not critical) that attenuates (via the skin effect) microwave signals very rapidly and prevents them from entering or exiting. (and these copper sheets also prevent lower frequency signals from entering or exiting due to their Faraday Cage effects) Typically these buildings have public lobbies. The hallways leading to these public lobbies are usually constructed with special waveguides that prevent electromagnetic waves from propagating into or out of those lobbies.

Answer 3

I don't know but logically I guess this would do it.

Let's take the monitor first,
Each character has a different pixel profile. Monitor the moving radiation change and transpose the xy values into letters or numbers etc.
Now to the phone
That is transmitting on a fixed wavelength where the varying signal is in digital form. Find the wavelength and down load the signal and reconstruct.

Answer 4

Hi. It's also possible in practice. The keyboard is a much better source of decryptable info than the monitor. Each time a key is pressed it a) make a distinctive sound for inter-office monitoring and b) emits an electronic signal to the CPU. A detector can be made to listen for either. (Design it yourself!)

Answer 5

radiation that incorporate the waves that have the two the characters of a magnetic container and an electric powered container is an EM wave case in point gentle distinctive from a wave in a string

Answer 6

I think Cirric answered most of your question...but what if you can't get to install some emitter on the comp. in question....I guess i'm rather asking a question than answering one :)

Answer 7

dont know