Countersurveillance

Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Countersurveillance refers to measures undertaken to prevent surveillance, including covert surveillance. Countersurveillance may include electronic methods such as bug sweeping, the process of detecting surveillance devices, including covert listening devices and visual surveillance devices. More often than not, countersurveillance will employ a set of actions that, when followed, reduce the risk of surveillance. 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. Professional sweeping devices are very expensive. Low-tech sweeping devices are available through amateur electrical magazines, or they may be built from circuit designs on the Internet. Sweeping is not 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.