A couple of British software engineers have just discovered that your iPhone (if, you know, you happen to have one) keeps a permanent detailed record of your movements. Whenever you sync your phone with a computer, the record goes there, too. They’ve written some quick and dirty software to demonstrate. In a matter of seconds, you can see every place you’ve been:

This particular map isn’t me; it’s one of them. I suddenly feel a little queasy about showing everyone where I’ve been. Which is, of course, the point.

They are Alasdair Allan, an astronomer at the University of Exeter, and Pete Warden, formerly of Apple and now living in Boulder. They happened to be collaborating on some projects for visualizing location data—for example, making maps of radiation levels in Japan—when one of them stumbled across a hidden iPhone file containing tens of thousands of data points: latitudes, longitudes and timestamps to the nearest second. The file is not encrypted; it was fairly easy for them to figure out.

They have no evidence that the data are transmitted to Apple or anywhere else. But there’s a problem nonetheless, and they sum it up nicely:

This data is stored in an easily-readable form on your machine. Any other program you run or user with access to your machine can look through it…. By passively logging your location without your permission, Apple have made it possible for anyone from a jealous spouse to a private investigator to get a detailed picture of your movements.

They have posted a helpful explanation and FAQ. Their software displays your movements as an animated, zoomable movie. If you’re like me, you might actually take some guilty pleasure in seeing all the places you’ve been and when. Then afterward you can start to worry.

File this under, Who Owns Your Information?