Bluetooth Big Brother tracks thousands, using mobiles and laptops

A Big Brother network of hidden scanners is monitoring hundreds of thousands of Britons without their knowledge, it emerged yesterday.

Scientists track people walking around cities, using the Bluetooth signals from their mobiles, laptops and handheld computers.

Scanners in bars, offices and universities register nearby Bluetooth devices and send the information to a central database.

The Cityware project, which is funded by £1.2million of taxpayer's money, started in Bath three years ago and is designed to chart how pedestrians use city centres.

It will be used to improve their design, learn how people use public transport and shops and work out how epidemics can spread.

There are thousands of scanners globally, of which 1,000 are actively tracking passers-by at any one time. Three-thousand people in Bath were monitored in one weekend alone.

The signals they get from phones and laptops do not reveal personal information. But critics say the signals can contain the owner's details.

Bluetooth devices use radio signals to communicate with each other. If Bluetooth is switched on, a gadget will broadcast its name and ID number to anyone within 100 yards.

The name can be changed by the owner and often includes their own name, email address or phone number. The scanners convert the data into maps showing the movement of people over time.