Pete Warden and Alasdair Allan, a pair of security researchers, have made a discovery about Apple Inc.'s (AAPL) popular iPhone and iPad devices.  According to an in depth study they performed, Apple not only tracks its iPhone and iPad users' every move, but it stores that information in a local file.

According to the researchers, the feature popped up with the release of iOS 4.  

It has been known for some time that the iPhones collect data on their user's position and uses it to target iAds at them.  Apple had received a great deal of criticism for doing that.  But nobody knew just how far Apple had gone in violating its users’ privacy -- until now.

The file is found in both iPad and iPhone.  It even transfers when users purchase a new device.

Describes Mr. Allan in an interview with British news site Guardian, "Apple might have new features in mind that require a history of your location, but that's our speculation. The fact that [the file] is transferred across [to a new iPhone or iPad] when you migrate is evidence that the data-gathering isn't accidental."

The pair discovered the data file on accident.  Recalls Mr. Warden, "We'd been discussing doing a visualization of mobile data, and while Alasdair was researching into what was available, he discovered this file. At first we weren't sure how much data was there, but after we dug further and visualized the extracted data, it became clear that there was a scary amount of detail on our movements."

Strangely, Apple does not appear to be directly transmitting the data to a central location, so it’s unclear why exactly its storing it locally.  The decision to track and store a users' location in a local file is highly unusual.  Mr. Warden and Mr. Allan searched for similar code in Google Inc.'s (GOOG) open source smart phone/tablet operating system, Android, but could not find one.

States Mr. Warden, "Alasdair has looked for similar tracking code in [Google's] Android phones and couldn't find any.  We haven't come across any instances of other phone manufacturers doing this."

He says that Apple has committed a shocking breach of privacy.  He comments, "Apple has made it possible for almost anybody – a jealous spouse, a private detective – with access to your phone or computer to get detailed information about where you've been."

The file is also transferred to the user's computer when they sync their device.  This raises the possibility that a computer thief or someone with access to the user's laptop could track their recent whereabouts.

Simon Davies, director of the pressure group Privacy International, agrees that the implications of the discovery are alarming.  He states, "This is a worrying discovery. Location is one of the most sensitive elements in anyone's life – just think where people go in the evening. The existence of that data creates a real threat to privacy. The absence of notice to users or any control option can only stem from an ignorance about privacy at the design stage."

The data is stored any direct agreement or approval from the user.  However, iTunes' 15,200-word terms and conditions contract does state:

Apple and our partners and licensees may collect, use, and share precise location data, including the real-time geographic location of your Apple computer or device. This location data is collected anonymously in a form that does not personally identify you and is used by Apple and our partners and licensees to provide and improve location-based products and services. For example, we may share geographic location with application providers when you opt in to their location services.

If users opt out, they are banned from iTunes.

Apple refused to comment on why its devices are monitoring its users' every move.

For Apple users, about the only way to provide yourself with a degree of safety is to try to encrypt the file.  Details can be found at a webpage the pair has been set up.  More details can also be found in an article the pair authored for the site O'Reilly's Radar.

The pair are presenting their findings later today, in detail, at the Where 2.0 conference in San Francisco.