Apple's Secret Location File: Is it Just About Cell Towers?

The iPhone location scandal dominated the tech news today. While early reports seemed to indicate that all iPhone 4s and 3G-enabled iPads were keeping precise logs of everybody’s location over time, the reality that emerged over the course of the day is a bit more complicated. Atlanta-based tech blogger Will Clarke took a closer look at the data tonight and argues that Apple is decidedly not keeping a log of the phone’s location in this secret file, but is only storing the location of cell towers.

Clark plotted the raw data from the file on his phone (the iPhoneTracker app’ only shows an approximation to obscure the exact location from snoopers) and compared it to GPS data he collected during a bike ride. The discrepancy between the two data sets leads him to believe the phone is only storing the locations of cell towers it gets in contact with.

His conclusion: “The only thing that makes sense is that the iPhone is actually storing the locations of the cell phone towers that it communicates with. My guess is that the iPhone uses this data to help it locate cell towers if it is in the same location again in the future.”

What’s Apple Really Storing? Cell Tower Locations

After reading this, I took a closer look at the data on my phone and I think I can back his theory up with what I found. Here is a plot of data from the iPhoneTracker app from my recent trip to Maui. You can see that the plot actually puts me on a neighboring island at times – likely because it get a ping from cell towers there while we were on the beach.


So why is Apple storing this data then? It doesn’t look like the phones actually transmit any of this data back to Apple’s servers. Unless this is just sloppy programming and a developer forgot to set a function to erase a temporary log file (not something Apple is known for), there must be some reason for this file to exist. My best guess: the iPhone relies on this database to speed up GPS reception without having to ping Apple’s servers to do so (which makes a difference, especially now that Apple has moved to its own location database).

Still Creepy

Whatever the reason for the file’s existence, none of this absolves Apple from the responsibility to at least encrypt this data. Even though the low accuracy does make the data somewhat less useful for those who want to use it for nefarious purposes, it can still show what town you were in and when. That’s not quite as bad as being able to place you on a specific street at a specific time, but even the low-resolution data still has serious privacy implications.