TSCM (Technical Surveillance Counter-Measures) is the original United States military abbreviation denoting the process of bug-sweeping or electronic countersurveillance. It is related to ELINT, SIGINT and Electronic countermeasures (ECM).

The United States Department of defence defines a TSCM survey as a service provided by qualified personnel to detect the presence of technical surveillance devices and hazards and to identify technical security weaknesses that could aid in the conduct of a technical penetration of the surveyed facility. A TSCM survey will provide a professional evaluation of the facility's technical security posture and normally will consist of a thorough visual, electronic, and physical examination in and about the surveyed facility.

The advent of multimedia devices and remote control technologies allow huge scope for removal of massive amounts of data in very secure environments by the staff employed within, with or without their knowledge. Even PlayStation Portables (PSPs) have wireless connectivity and optional storage capacity. Therefore connection and forward on receive over 54 Mbit/s wireless for hundreds of meters is achievable.

Radio Frequencies

Most bugs emit some form of electromagnetic radiation, usually radio waves. The standard counter-measure for bugs is therefore to "sweep" for them with a receiver, looking for the radio emissions. Low-tech sweeping devices are available through amateur electrical magazines, internet spy shops but sweeping with these cheap devices is no way foolproof. Advanced bugs can be remotely operated to switch on and off, and some even rapidly switch frequencies according to a predetermined pattern in order to make location with sweepers more difficult. Only top of the range state-of-the-art professional sweeping devices will have the ability to detect modern surveillance devices.

The non-linear junction detector, or an NLJD, is a device that illuminates a small region of space with high-frequency, RF energy. Any "non linear junction" in the vicinity -- for example, and particularly, the p-n junction -- will receive this energy, and because of the non-linear nature of the junction, it will rectify it, re-emitting some of it on multiples of the illumination frequency (2nd & 3rd harmonic frequency). The detector has two sensitive receivers tuned for these harmonics, as well as appropriate processing and displays to make their presence known to the user of the device.