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In discussing "bugs", the most often thought that comes to mind is of a miniature transmitter placed behind a picture frame, in a potted plant, in a desk or perhaps in a floor lamp. But, have you ever really considered what a "bug" is, or how it operates? What frequencies does it operate on?

A "bug", in most instances, is a transmitting device. It consists generally of a microphone, audio amplifier circuit, a radio frequency an circuit, an antenna and a power supply. Size will depend on the application, ranging from the size of a pack of cigarettes to as small as a pencil eraser. Commonly, most are about the size of a quarter which includes the battery.

As for the range in frequencies, the "bug" can be built to operate anywhere from below the standard AM broadcast radio band to above the commercial microwave frequencies of 40 GHz. The biggest threat is from those operating from approximately 70 MHz to about 300 MHz, simply because it is easier to build them for these frequencies.

Generally speaking, these frequencies use less power to operate. The antennas are shorter, component selection is less critical and better transmitting range is realized.

One of the things most often asked is, "where is the greatest threat when looking for a "bug." The largest percentage of devices are found in the "amateur spy band" of approximately 70 MHz to 130 MHz. Why? Simply because more devices are constructed and available which work in these particular ranges.

It takes no sophistication and very little money to construct these transmitters. Kits can be bought for $30.00 and up and contain about $5.00 worth of parts. They and can be constructed in as little time as a couple of hours (taking time out for a coffee break) and can transmit a signal in excess of a mile. A little more sophisticated are those devices in the 150 MHz to 300 MHz range, only because more care must be taken in their construction, but they are equally as effective.

Most signals encountered will be in clear text, either AM or FM. Where we start running into problems is when the intelligence on the signal is "manipulated". This comes about by the various means of modulating a signal, such as transmitting an AM carrier with an FM sub-carrier, or an FM signal with an AM sub-carrier.

Another step up the line is the pulse position or pulse amplitude method of modulation. the top of the line is generally considered to be "spread spectrum signals" in which the signal is spread over a very wide frequency range versus a very narrow frequency range for other signals.

The "bugs" sensitivity and transmitting range will be directly proportional to their size. The smaller "bugs" will have a limited range. Eavesdroppers have been known to employ relay transmitters. A relay transmitter receives the weak signal from the target area and automatically re-transmits the signal to a more distant point.

A sophisticated approach to bugging is the remotely controlled "bug". This type of "bug" is used to foil detection and to conserve battery life.

If you have any indication that a "bug" has been planted in your area of responsibility you should contact a reputable countermeasure firm that has the expertise and technical equipment to detect and neutralize a technical attack.
   
 

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