Electronic bugs in surveillance
Electronic bugs are covert listening devices designed to capture conversations without detection. These bugs can be categorized into four main types: radio-transmitting, nonradio, telephone-based, and reflection-based. Radio-transmitting bugs are the simplest to deploy and can transmit audio signals to remote devices, while nonradio bugs present more challenges in detection as they do not emit radio waves. Telephone-based bugs operate through phone lines and can be discreetly installed, allowing for eavesdropping without alerting the user. Reflection-based bugs utilize radiation, often through lasers, to pick up sound vibrations from reflective surfaces.
The significance of electronic bugs in surveillance has prompted the development of various bug detectors, which have evolved to match the increasing sophistication of the bugs themselves. Detection methods range from basic radio receivers to advanced spectrum analyzers and nonlinear junction detectors, each employing different technologies to identify signals from listening devices. Bug manufacturers continuously innovate techniques to evade detection, adding layers of complexity to the ongoing battle between surveillance technologies and detection measures. Understanding the capabilities and limitations of these devices is essential for grasping the implications of electronic surveillance in modern contexts.
Electronic bugs in surveillance
DEFINITIONS: Bugs are hidden microphones used to listen in on conversations surreptitiously; bug detectors are devices designed to find any bugs in a given area.
SIGNIFICANCE: The invention and subsequent deployment of bugs in covert surveillance was quickly followed by the invention of bug detectors. Over time, the makers of bugs have created increasingly sophisticated devices in their attempts to evade the ever-widening scope of detection achieved by competing detectors.
The designs of the listening devices known as bugs are limited only by the imaginations of the designers. Bugs can be broadly divided into four types: radio-transmitting, nonradio, telephone-based, and reflection-based.
Radio-Transmitting Bugs and Their Detection
The simplest type of bug to place, and the simplest to detect, is the type that functions by transmitting a radio signal to the listener or, more often, to a remotely located tape recorder. Such a bug can be placed quickly because it requires no installation of wires; in addition, the user can change recording tapes without having to gain access to the bug itself. Bugs of this type can be extremely small. They can operate off battery power or, if located in an electrical or telephone outlet, can draw power from the outlet and operate indefinitely.
The simplest detectors for radio-transmitting bugs are broad-spectrum radio receivers. These report, by indicator lights or audio hum, whether radio signals, at any frequency, are being emitted near them. In practice, the sensitivity of a radio receiver being used for bug detection must be lowered so that it does not report ordinary radio and television signals. Once the sensitivity is lowered, the broad-spectrum receiver has a very short detection range for bugs, so the user must conduct a careful sweep with the detector to ensure that no bugs are missed.
Better than the broad-spectrum receiver is the frequency counter, which displays the frequency of a radio signal upon detecting it. A great (and quite costly) improvement over both the broad-spectrum receiver and the frequency counter is the spectrum analyzer, which not only detects all radio signals but also displays their frequencies and strengths on a bar graph. The user can thus ignore powerful but innocent transmissions—radio and television stations—and focus on others.
A more sophisticated search for radio bugs requires two tools. The first, an audio emitter, is placed in the room being swept and emits a loud audio signal on a single frequency. The other tool is a radio scanner that automatically sweeps all frequencies within its range, briefly listening to each frequency. It stops and sounds an alert if it hears a radio transmission containing the audio signal given off by the emitter.
Bug manufacturers attempt to evade these detectors with technology such as burst transmission, in which the bug itself records signals, compresses them, and then sends them in brief bursts, five or ten minutes apart. Another device that can evade such detectors is the remotely controlled bug, which is turned on only when a conversation is to be overheard and thus is likely to be missed in general sweeps.
Nonradio Bugs and Their Detection
Detecting bugs that do not transmit radio signals is much more difficult, but makers of bug detectors have evolved tools aimed at these as well. The simplest is an ultrasound generator, which, under the right conditions, can cause a microphone’s diaphragm to vibrate and give off an audible sound. This kind of detector can find hidden tape recorders because most of them, when running, give off faint ultrasonic signals that can be picked up by specialized listening devices.
The most sophisticated tool for seeking nonradio bugs is the nonlinear junction detector. This device transmits a microwave signal that is reflected back (at a slightly different frequency, known as a harmonic) by transistors and similar electronic components used in bugs. This type of detector will even spot bugs that are not transmitting. Bug makers seek to evade these detectors by encasing their bugs in metal shielding that blocks the microwaves.
Telephone- and Reflection-Based Bugs and Their Detection
Telephone-based bugs, also known as infinity transmitters, rely on devices, usually installed in telephones, that allow them to transmit over telephone lines and allow the listeners to call in without the telephones ringing. Such devices can be detected by electronic tests of the telephone lines.
A reflection-based bug functions by reflecting radiation off an object that serves as a diaphragm. Sound causes the object to move, and the movement is shown in the reflected radiation. At a simple level, an infrared laser can be reflected off a windowpane to reveal conversations inside the room where the window is located. During the Cold War, the Soviets used a more complex reflection-based system to bug the US embassy in Moscow. Soviet schoolchildren presented the embassy with a gift: a wooden carving of the Seal of the United States in which was hidden a metal diaphragm with a tiny antenna. When a microwave beam was directed at the seal, the antenna absorbed the energy and radiated it back, varying with the audio in the room. The bug was operational for seven years before it was accidentally detected.
Searches for reflection-based bugs center on searches for the beams used to radiate them, which are usually infrared or microwave beams. Such searches are complicated by the fact that the beams are radiated only when the bugs’ users are attempting to listen in on conversations.
Bibliography
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