T 0.13 Intercepting Compromising Emissions

Electrical devices emit electromagnetic waves. In cases of equipment which process information (e.g. computers, displays, network coupling elements, printers) this radiation can also carry the information currently being processed with it. Such information-bearing radiation is called expositional or compromising emissions. An attacker, for example in a neighbouring house or in a vehicle parked in the proximity, can try to intercept this radiation and to reconstruct the processed information carried there. The confidentiality of the information is this way called into question. A possible motive for such an attack is industrial espionage.

The limiting values in the Act for the Electromagnetic Compatibility of Resources (EMVG) generally do not suffice to prevent interception of the compromising emissions. If this risk cannot be accepted, additional protective measures must therefore be taken.

Compromising emissions are not restricted to electromagnetic waves. Useful information can sometimes be retrieved from sound waves produced by printers or keyboards, for example.

In addition, it has to be taken into account that compromising emissions can be, in some cases, caused or amplified by the external manipulation of devices. If a device is exposed to radiation with electromagnetic waves, it may occur that the reflected waves carry confidential information.