Enable Passcode Lock on Your iPhone
The most basic precaution you can take is to enable passcode lock and set it to automatically engage
after a brief period of inactivity. By default, a passcode is not required to unlock the iPhone. Most people
would put off this security measure for ease of use and convenience. However, the truth is that once you
have it enabled, it becomes second nature and you would not notice any difference. It is recommended
that you set a strong passcode. In the event of a physical theft, this will increase the effort required
to compromise your iPhone. Also, for some other security applications to work such as Find My iPhone,
a passcode is mandatory.
How to setup a passcode lock
1.  Navigate to Settings > General > Passcode Lock.
2.  Tap Turn Passcode On.
3.  You will be prompted to enter a four-digit passcode twice. Choose a passcode that’s difficult to
guess. See the guidelines on choosing hard passcodes below