One of the best way to prevent your details on iPhone/ iPod Touch/iPad (iOS device) from being viewed by people you don’t want it to be viewed by is to set a passcode on it. Follow some simple steps below and get your iOS device protected.
1. From your home screen, select “Settings” –> “General” –> “Passcode Lock”
2. Select “Turn Passcode On” –> Set a passcode –> Re-enter passcode
…from here, you can change password types like, using simple passcode (4 digit numbers) or more complicated one for better protection. You can also set the passcode required time, eg: Immediately after you lock your device, after 1, 5, 15 minutes,… or how ever you like it.
Still not satisfied? Check out this article about an iOS app called My secret Folder that let you hide and protect your files!
Hide your files 