Bluetooth tracking: is there a danger to civil liberty?

Last week the newspapers revealed that the residents of Bath were being surreptitiously tracked via Bluetooth and their mobile phones. The scheme's operators have defended themselves by saying that Bluetooth data is anonymous: it isn't linked with you in any reliable way. So is there a problem?

Yes - but not a terribly serious one. Although there is no fool-proof way to link Bluetooth data with an individual, there are plenty of cases where that link can be made:

* If you set your phone's name to your own name. Admittedly, such people probably know they're broadcasting this data and are happy to do so.
* By statistically linking the phone's movements with that of a person. If they matched lists of employees against home addresses... there is a reasonable chance they can identify individuals.

Simon Davies, of human rights watchdog Privacy International, said: 'This could become the CCTV of the mobile industry... It would not take much to make this a surveillance infrastructure over which we have no control.'

This is an over-reaction. One good thing about Bluetooth is that you do have control of it. You can switch it off, or switch it to be private. In fact unless you use a Bluetooth headset, you should switch it off: Bluetooth drains the battery power from your phone.

Now the thing is that you are already being tracked. If you live in a city, your mobile phone can be tracked to ~500m by looking at which transmitters it talks to. This data is kept by the phone companies and occasionally used by the government, e.g. in police investigations.

F.A.Q.

"What can they find out about me?"

The Bath system can only detect your position. It cannot detect anything about you if your Bluetooth is switched off.

The system uses a set of detectors. When you pass by a detector, it notes the time and your Bluetooth ID. This gives a list of "sightings" which can be used to plot a trail of your movements. Bluetooth detectors have a range of about 10m, cost ~£200 and require a power supply to run. They can't be scattered just anywhere, and the system can only find you if you're nearby to one.

"Do I have Bluetooth on my phone?"

Probably - most mobile phones do, especially if you got it within the last few years.

"Is my Bluetooth on?"

Bluetooth is often on by default. The phones I'm familiar with have a blue light which flashes periodically to indicate when Bluetooth is on. To be sure, find the Bluetooth settings in your phone's menu. tags: group:frontpage bluetooth tracking civil-liberties profiling