Setting a simple passcode for your iPhone will encrypt much of your valuable data, such as email and attachments. Even if a thief jailbreaks your phone, the data remains protected by the passcode you’ve set.
Turns out there’s a loophole. If you set your passcode when your iPhone (or iPad) was using iOS 3 and you upgraded to iOS4, your data might not be encrypted.
Security expert Rich Mogull explains this in detail in the lead article in today’s issue of TidBITS.
Here’s how to tell if your passcode is really working:
Go to Settings > General > Passcode Lock. Enter your passcode to reveal the Passcode lock screen, and scroll all the way to the bottom of that screen. In dark blue letters, at the very bottom, you should see the phrase “Data protection is enabled.”
If you don’t see that, follow Rich’s directions in “Make Sure Your iOS Device is Really Encrypted.” He’ll also point you to an Apple support article on the topic.