Business Espionage: GSM Bugs Are Mini Cell Phones in Disguise

(from a seller's website in the UK)
GSM bugs are also known as mobile phone bugs and infinity bugs. Based around mobile technology, these devices provide a discreet listening facility with an unlimited distance.

Click to enlarge.

Up until a few years ago radio frequency transmitters were relied upon to provide an eavesdropping solution, albeit over only relatively short distances, generally up to about 800 metres line of sight. These devices are still available, but have been outlawed by OFCOM legislation and are therefore not legal to sell into the UK or operate in the UK without a radio broadcast licence. GSM Bugs use the existing GSM network as a transmission tool.

When they fist became available, the GSM bugs were literally modified mobile phones that auto-answered silently to open up the microphone and listen into the surrounding environment. These devices are still available today and some dedicated (dead phone) units have had enhanced microphone adjustments to make them more attuned to pick up sounds in a wider area, turning them into dedicated listening devices.

As the technology has moved on, these eavesdropping devices have become smaller and more sophisticated. They are really only restricted in size at present by the battery size, however, some of the latest units are built into mains powered devices such as multi-plug adapters and mains sockets, thereby making them invisible to the naked eye and with no power consumption restrictions.

Some of these eavesdropping devices are obviously for the UK market.
Bugs for other electrical standards are also available. 

Do you have electrical extension strips in your office?
Have they been inspected and sealed by a TSCM specialist? 
~Kevin