Researchers say iPhones can track users' movements
Apple iPhones and 3G iPads are secretly recording and storing details of all their owners' movements, researchers claim.
Location data is kept in a hidden, unencrypted file according to security experts Alasdair Allan and Pete Warden.
With the right software, it can be used to map exactly where a person has been.
The BBC's technology correspondent Rory Cellan-Jones explains.