There are many types of listening devices available including hard wired, radio frequency, acoustic audio and optical bugs. Here we examine some of the most frequently used listening devices in the corporate espionage arena.

GSM Bugs

Perhaps the prolific listening device today, GSM bugs operate in exactly the same way as a mobile phone

and a perpetrator can in effect, dial in and silently listen to a conversation from anywhere in the world!

A GSM bug can be a small black box that can be discreetly hidden in a room or it can be a purpose built device such as a mains adaptor, a power strip adaptor, a PC mouse or a phone charger for example. These are everyday objects that one would expect to find in an office, for example, but which could harbour a dangerous secret!

High quality GSM bugs are readily available to buy online and from some high street shops and prices start from under £10.

Miniature Voice Recorders

Readily available from online stores, miniature recording devices such as Edic-mini recording devices and those disguised as USB drives or credit cards are discreet audio recording devices designed to be easily hidden or pass undetected by the unwary target. Their use is limited by their battery life and storage, but in many situations they can be just the weapon an infiltrator needs while being affordable and delivering high quality audio.

Mobile Phones as Bugs

Mobile phones themselves can be used as bugging devices. They can be programmed not to vibrate, ring or show any outward signs that they are being called. They then auto-answer and the caller can listen in to conversation within the room.

This type of attack can either be done on a target phone which the perpetrator would then leave somewhere in the vicinity of the conversation they are targeting, or it could be done illicitly by sending someone an email or text with an attachment which, once opened, would download the necessary software onto the target phone. The phone can then be controlled by the hacker who can remotely switch it on and listen from any other mobile phone anywhere in world.

In addition, a report by Computerworld claims that some new Smartphone apps are using your phones microphone and camera to gather data about you! A new class of app has emerged that uses the microphone built into your phone as a covert listening device. The apps try to alleviate privacy concerns by saying they only record sound patterns, not actual sounds or conversations. But in the end, the technology is there, and it’s being used to some extent.

As a precaution you should take care when downloading apps as you could easily download malware and so only download from your service providers website. Also be cautious of using Wi-Fi connections. Unsecured networks could mean that someone else using that network could see what you’re doing on your phone.

Even when a GSM function is disabled on a Smartphone, the in-built camera can still be used as an eavesdropping device. Smartphones can be used to record video and take photos, stealing product information prototypes etc. As it is virtually impossible to buy a mobile phone device without a camera, this is a threat which should not be ignored.

Radio Frequency (RF) Transmitters

A Radio Frequency (RF) bug involves the placing of a radio transmitter in a room and listening within range using a receiver. One of the most infamous examples of the use of a RF bug is the “Great Seal Bug” story, when in 1952 a RF listening device was found in a carved wooden seal that had been presented to the US Embassy in Moscow and had hung in the Embassy since 1946.

RF bugs can be incredibly small and can be concealed in just about anything including skirting boards, picture frames, plugs etc. Relatively inexpensive and easy to use, you need a receiver to listen to them.

Radio frequencies are given off by nearly all spying devices, and these radio frequencies can be detected with specialist equipment as used by TSCM engineers. Different types of bugs give off a large range of frequencies and specialist equipment is required to check the entire RF spectrum. Basic RF detectors, that can be purchased relatively cheaply, will only be able to detect limited frequencies and will give you a false sense of security, and so its always best to engage the services of a professional TSCM provider.

Phone Taps and Phone Bugs

Two terms which are often interchanged but in fact refer to two separate types of attack are Bug and Tap. The differences are:

Tap or Wiretap
This is a device placed on the telephone system and is designed to intercept telephone conversations, i.e. if no call is in place then the tap is inactive.

A bug is used to listen to room conversation but may use the telephone or line as a facilitator of this. This type of attack means that all conversation in the area is susceptible to being overheard by the attacker and not just telephone calls.

Optical Devices

Optical devices convert audio signals into transmitted light pulses which are then converted back to audio signals by a receiver. One example of this is the laser attack whereby a laser beam is projected onto a surface, such as a window, and the vibrations detected are converted into audio signals. Laser attacks are difficult and expensive to conduct.