Two trends in cellphones are combining to create a new security risk. On the one hand they are becoming more powerful, and more like computers. On the other, they are universally relied upon.
As Nokia's cellphone anthropologist puts it, all over the world people take three things with them when they leave the house: keys, money and phone.
The result: an easily lost or stolen device with a lot of private and sensitive data on. And a book released this week called iPhone Forensics (published by O'Reilly) gives an insight into the surprising amount of personal information a smartphone can store. Or give away.
Here's a list of ways in which your iPhone could release sensitive data about you - I image much the same could be gleaned from other similarly advanced handsets.
Past keyboard input - "Nearly everything typed into the iPhone's keyboard is stored in a keyboard cache, which can linger even after deleted." That will include user names, passwords and much more.
Deleted images from the photo library, camera roll and web history can sometimes be recovered.
Deleted address book entries, contacts, calendar events can also sometimes be recovered.
"Exhaustive call history, beyond that displayed, is generally available." The last 100 entries can usually be found, and deleted call records recovered.
Map tile images, direction lookups and location coordinates from the Google Maps application. In effect, where you've been or may be planning to go.
Deleted browser cache can usually be recovered, revealing the websites you've visited.
Cached and deleted emails, SMS messages and other communications can be recovered, along with information on when they were sent and who to.
"Deleted voicemail recordings often remain on the device."
The rest of Jonathan Zdziarski's book details the tools and techniques that will give you access to all those. Apart from an iPhone, all you need is some free software.
Police forces already use records recovered from GPS units to solve crimes. Techniques like those in Zdziarski's book look set to become a big part of the work of police and criminals alike.