The threat of information theft by reception of electromagnetic radiation from RS-232 cables

Research into the possibility of picking up the electromagnetic radiation originating from video display units (VDUs) made clear that this type of information theft can be committed very easily [1]. It is not only this type of equipment which is vulnerable to interception at a distance; experiments on eavesdropping RS-232 cable signals prove that it is possible in some cases to intercept data signals running along an RS-232 cable, by picking up and decoding the electromagnetic radiation produced by the cable. This report gives the results of these experiments and research into the underlying mechanisms. These results show, that compared with the VDU case, RS-232 eavesdropping has significantly different consequences with regard to information security. Electromagnetic radiation arising from RS-232 cables may contain information which is related to the original RS-232 data signals. The seriousness of eavesdropping risks is shown by estimates of bit error rates feasible with a standard radio receiver as a function of the separation distance. In addition to this, results of experimental eavesdropping are presented.