Bugging

A 'bug' is the common name for a covert listening device, usually a combination of a miniature radio transmitter with a microphone. The use of bugs, called bugging is a common technique in espionage and an increasingly common one in police investigations.

A covert listening device on a person (also known as a "wire") is often used to gain evidence involves a radio transmitter, but there are many other options for carrying a signal; you can send radio frequencies through the main wiring of a building and pick them up outside, you can pick up the transmissions from a cordless phones, and you can pick up the data from poorly configured wireless computer networks or tune in to the radio emissions of a computer monitor.

Bugs come in all shapes and sizes. The original purpose of bugs was to relay sound. Today the miniaturisation of electronics has progressed so far then even TV Amateur bugs are usually the size of a cigarette packet. Professional bugs can fit into pens, calculators and other commonplace items. Some are only the size of small shirt buttons - but the power and operation life of the smallest bugs is very short.

The devices used by persons or organisations without the funding to buy professional equipment are (this space should have a word but it wasnt included). Another great problem with modern technology is the development of 'wireless' appliances. To be 'wireless' a device must transmit information, either by radio waves or infra-red light, and this potentially makes all the information sent via that link available to others. Radio waves are the best option, but even infra-red can be picked up through a window. Some wireless devices, such as wireless computer networks, do encrypt transmissions, but the standard forms of encryption are weak.

Wireless devices, be it a wireless keyboard or a wireless telephone, should not be used in any environment where sensitive information is handled.

Bugs emit 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. There are low-tech sweeping devices available, through amateur electrical magazines, or that can be built from circuit designs on the Internet. But sweeping is not fool proof. Advanced bugs can be remotely operated to switch on and off, and some even rapidly switch frequencies according to a pre-determined pattern in order to make location with sweepers more difficult. You may also be bugged, but you don't detect it when you sweep because it's run out of power.

The other problem are those bugs that do not emit radio waves - they are very difficult to detect. Bugs are a technical solution to a problem - remotely listening to people's conversations. A simpler option is simply to record the conversation on a normal recording machine. There are a number of options for this:

• Pocket sized devices, either worn or carried in baggage, linked to a small microphone that's usually mounted on the surface to pick up the audio. Digital recording devices, such as minidisc or the latest palm-sized camcorders, also give very high quality recordings in a very small device.

• Larger recording devices hidden in the room, for example above suspended ceilings. These are popular in workplaces for monitoring staff.

• Ultra directional microphones. These are like the microphones you see on camcorders, or carried by sound technicians. They are constructed to receive signals only from one direction. The most high-tech directional microphones can eavesdrop on conversations from a hundred metres away or more.

• Laser microphones. These are very expensive and highly technical to operate. You bounce a laser beam of a window, or off some object near the conversation you want to hear that resonates (for example, a picture on a wall). Any object which can resonate/vibrate will do so in response to the pressure waves created by noises present in a room. The electronics detect the minute difference in the distance travelled by the light to pick up this resonance, and reproduce the sound causing that resonance.

If a microphone is hidden in a room it is almost impossible to detect it. This is because it has no radio emission. Very sensitive equipment could be used to look for magnetic fields or electrical noise emanating from the recording equipment. This is because the computerised/digital technology in digital tape recorders emits characteristic electrical noise. But if the place being monitored has lots of computers, photocopiers and other electrical equipment installed that would be very difficult. Older analogue equipment is very difficult to detect.

Bugging devices in EU headquarters

Electronic bugging devices were found in March 2003 at offices used by French and German delegations at European Union headquarters in Brussels. Devices were also discovered at offices used by other delegations. The discovery of the telephone tapping systems was first reported by Le Figaro newspaper, which blamed the US.