Transient signal attacks (TEMPEST, sometimes said to be an acronym for Transient ElectroMagnetic Pulse Emanation Surveillance Technology) analyze leaking signals to try to obtain information of interest. This could include the sound of keystrokes to determine what is being typed, or it could be the electromagnetic signals your monitor leaks in order to remotely reconstruct what it displays. The military protects the most classified secrets from this sort of attack by storing the electronics that are used to display them in SCIFs , Secure Compartmentalized Information Facilities. These are usually rooms that are pretty much hollowed out metal boxes, with thick metal walls completely surrounding the machines and people inside of them. You can find pictures of them if you google around. You can also buy specialty equipment that is shielded to some extent from transient signal leakage, although it tends to be pretty expensive. You could take some simple measures to make this sort of attack more difficult though, for example if you have a basement it will probably shield you more adequately than you would be at a coffee shop. Another thing to take into consideration is that a lot of information tends to leak into the power grid as well. I think that transient signal attacks are really interesting from a theoretical perspective. They have been used in practice by the FBI, but the only case I know of where they did this was against a Russian spy ring. They are probably more commonly used by intelligence agencies like the CIA etc. The thing about TEMPEST attacks is that the attacker needs to have already identified you to carry them out (since they need to be physically fairly close to you), and if the attacker has already identified you then it is pretty much game over anyway, TEMPEST attacks or not. So the best defense from this sort of attack is actually to maintain your anonymity. These attacks are more applicable to an intelligence agency trying to protect its information secrets from foreign intelligence agents, than they are to a drug dealer trying to protect the content of their communications and computer system. Because the foreign intelligence agency may know where the secrets are stored and not be able to get them covertly due to the SCIF or whatever, but if the feds know where the drugs are stored they are just going to kick the door down or do covert surveillance in less technically sophisticated ways.