Security researchers have discovered that Apple's iPhone keeps track of where you go - and saves every detail to a secret file on the device which is copied to the owner's computer when synchronised.

The file contains the latitude and longitude of the phone's recorded co-ordinates along with a timestamp, meaning that anyone who stole the phone or the computer could discover details about the owner's movements using a simple program.

For some phones, there could be almost a year's worth of data stored, as the recording of data seems to have started with Apple's iOS 4 update to the phone's operating system, released in June 2010.