The Spy Within. Are you bugged? Listening devices and hidden cameras.

Lately we've had a number of de-bugging cases, with people who suspect their home, car or business is being monitored by listening devices or hidden cameras. For convenience, we'll use the common parlance; bugs. 

What kinds of bugs are there?

All kinds. And then some. 

A listening device can be anything from a box the size of a pack of cards, to something the size of the head of a pin - and that's just the range of commercial available devices, not the range available to government and police. How big is largely a question of how much the listener is willing to spend.

A transmitting device (one which is being watched or recorded live at a secondary location) is no larger than a recording one, but its battery will generally need to be larger. It also needs an antenna, however this may not be obviously visible. If the use of the device is only short-term, however, the larger battery may still only be quite small.

For example, in certain circumstances we use transmitting cameras which are around half the size of a AA battery and voice recorders half of that size.

A hidden camera does not need to be larger than a listening device, but its power usage, especially if it's a transmitting camera, is higher. This affects battery size, or duration of use before the battery needs replacement. It may also lead to the device being hard-wired. 


Where a device will be is hard to say. Ideally, a bug is planted somewhere it's not likely to be, in order to make it harder to find. A professional will be aiming for this. If you have a bug hidden somewhere it is likely to be, odds are it was put there by an amateur. Having said that, are factors which make devices more likely to be in some places than others.

Cameras need to be able to see; a camera will need to be installed somewhere it has a line of sight at whatever it is that it's trying to see. In an office environment the best position for a camera is often the bird's eye, looking down on you. Take note of moved or scuffed ceiling panels, holes or marks in the ceiling, air vents or other dark places which have a view of you. Check light fittings, switches, power points and security sensors for signs of tampering.

In a high-noise environment, a listening device will need to be located closer to the target conversations. In a low-noise environment, a modern microphone placed anywhere in even a large room can be sufficient to make a good recording of even a whispered conversation.

Power Source

A recording listening device uses very little power. This means can easily run from a battery, which makes it possible to put it just about anywhere. Recording devices, especially those which only record when sound or motion is detected, can be hidden pretty much anywhere they fit.

A transmitting device (eg a camera) with a reasonable range uses quite a lot of power in comparison. If it's a long-term installation, this necessitates it being connected to a wired power source. This is most often the wire to a light, a switch or a power socket, which means detection of the device at these points is sometimes possible. Your ceiling, and under-floor-space are also often full of live wires which can be tapped to power a device.

Tracking Devices

If you notice someone is following you, but you can't work out how they keep finding you, they may be using a tracking device.  Such a device can be as small as a 20c coin or as large as a brick, depending on the purpose for which it was designed.

Devices used to help someone follow a vehicle range from GPS GSM devices which actively or periodically transmit their geographical location using the mobile phone network, through GPS units which record but to not transmit location, to 'beeper' radio beacon which transmit a simple audible (or inaudible) signal to a specialist receiver. It is also possible to use an entirely satellite-based device which does not need mobile-phone reception and works across most of the world. We use these devices primarily in remote-area surveillance and international asset tracking, including on yachts and international shipments.

For maximum efficiency, a GPS-enabled device needs a view of the sky, however many devices will provide adequate accuracy from a partially hidden location such as the under-side of a vehicle or the inside of a plastic bumper bar. 


In the majority of cases, if you have not consented to the use of the device, the installation or use of a listening device, hidden camera or tracking device will be unlawful.

It is our normal practice when sweeping for devices to stop once the first one is located and suggest that police be notified. This facilitates the preservation of the evidence of the crime. 

If a client does not wish to involve police when the device is found, we can continue sweeping for other devices, recording their locations, and taking photographs/video, and present this information as a report, declaration or affidavit, for your future use. In this circumstance, whether devices are removed or left in place is a tactical decision you will need to make.

Finding devices

At, among other things we use a wide-spectrum signal receiver and analyser to detect transmitting devices, a sensitive metal detector to find recording devices, and our good old fashioned eyes (sometimes via inspection cameras and reflecting-detectors) to find the rest. In some cases we also employ current-loss testing local narrow-band signal interference.

Who's listening?

If a device is transmitting, we can usually identify the approximate range it is likely to have, which may allow us to locate the receiver. This, however, is not always possible. An IP camera which is tapping into your home or work WiFi network may be impossible for us to trace, and a device with a strong transmission signal may create such a wide potential reception area that a search would be impossible.

The user of a recording device may sometimes be identified by us leaving it in place and covertly recording its collection. In many cases, even a transmitting system, if the installer is not aware it has been discovered, will be recovered at a later date and this may provide an opportunity to identify who has been watching.