Who Is Listening to Whom?
The Government Communications Headquarters located at Cheltenham, Gloucestershire employs many thousands of highly trained staff. Using sophisticated and expensive equipment they can eavesdrop on anyone, anywhere, at any time. It is part of the ultimate worldwide data-gathering body codenamed ECHELON, jointly run by the US, UK, Australian and New Zealand intelligence services. Its existence was officially acknowledged by the European Parliament last year.Every hour of every day, GCHQ and its close partner, America's National Security Agency, scoop up millions of communications -- speech, fax and computer data such as e-mail -- all over the world, using huge listening stations. In Britain, the two largest are Morwenstow, Cornwall and Menwith Hill, Yorkshire, both of which are run by NSA to overcome the legal restriction which forbids GCHQ to tap domestic calls in Britain.
To sort through the vast number of calls, GCHQ and NSA use dedicated ECHELON computers using an advanced word and voice recognition program called Dictionary to look for 'trigger words' of interest. This is simple because all today's communications, whether spoken or written, are transmitted as digital pulses which speak the same language as computers. Naturally, GCHQ and NSA are reluctant to give details of this illegal work, but as long ago as 1976, the NSA's Harvest computer system intercepted 75million calls a year, of which 1.8million were considered worthy of further analysis.
The Cray computers used by GCHQ and NSA in 1981 could read 320million characters a second, or 2,500 average size hardback books. Today's generation of computers have more than doubled this capacity. GCHQ has engineers permanently stationed at British Telecom's laboratories at Martlesham Heath, in Suffolk, who check any new product going on to the market so they know how to break into it. They would also know the various frequencies allocated to each cell so that recorded tapes could be re-broadcast.
Many thousands of calls using ordinary phones are intercepted every year under warrants issued by Government departments. The purpose is to detect serious crime, spying or drug smuggling. Intercepting a call over a normal landline is done at British Telecom's secret switching centre at Oswestry. Computers command the local digital exchange to duplicate the subscriber's calls over the Defence Communications Network (DCN) back to the nearest telephone tapping centre. No one, not even the local exchange, is aware that a line is being tapped.
Tapping a call illegally is very difficult and requires placing a bug in the telephone itself, physically breaking into the line (usually near the subscriber's house) or the help of a dishonest BT employee. However, long-distance calls are vulnerable to eavesdropping and civil servants' telephones have stickers reminding them of that fact. Calls which travel over 50 miles usually go by microwave, using towers dotted around the country. In the late 1970s, the NSA developed a satellite system called Rhyolite, which hovered over the Soviet Union and scooped up every telephone conversation made over microwave links, VHF and UHF radios and even the car telephones used by members of the government.
Mobile telephones first appeared in Britain in January 1985. Now several hundred million calls are made each week, split between the two major operators, Vodaphone and Cellnet. Of the several thousand transmitters located around the country, each cell station has a choice of 100 separate frequencies the subscriber's telephone uses at random. If the subsriber is moving around the country by car or train, the call is passed from one cell to another, switching frequencies automatically. Each mobile telephone carries its own identification (cell call), which is primarily intended to give computer details of each call for billing purposes although, of course, with the right equipment, it can also help trace a particular mobile phone. Even when switched 'off' mobile phones can still be tracked to within 50m of the carrier.
