If you don't want to be fraped by your friends or risk losing sensitive data to those with malicious intentions, or maybe you've just got something on there to hide, creating a phone lock is a great idea. These days you can even lock down individual apps for convenience or a layer of extra security (if your phone doesn't support this feature see How to password-protect Android apps).
Unfortunately, hacking a phone lock is simple, and with only a small amount of effort. I only have to look over your shoulder, inspect the smudge left behind by your fingertip from repeated unlocking, watch the way your fingers move as you unlock the phone or sneakily place a camera close by and I'm in. Or I could just guess, because chances are your passcode is 1234, 0000, 1379, 9999 or perhaps your birthday or that of your child's, or your lock pattern resembles a C, an X or maybe it's a square. (Read our advice on how to create a strong password.)
Researchers at Lancaster University, the University of Bath and China's Northwest University have discovered just how easy it is to hack these lock patterns, and the team successfully cracked 95 percent of 120 lock patterns within five attempts. They used smartphone cameras and a computer vision algorithm to work out the patterns, and found that even the most complex of designs were easy to hack - even when the screen was out of view.
Fortunately, it's easy enough to protect your phone lock pattern or passcode being hacked simply by covering over your screen and ensuring no-one is watching (cameras included) - exactly as you would at a cash machine. Then do your utmost to ensure that phone never leaves your side.
Should your phone get into the wrong hands, you can still remotely secure it from hackers. Using Android's Device Manager or Find My iPhone you can lock and even erase its contents, but you'll need to set it up in advance. Also see: How to use Android Device Manager and How to use Find My iPhone.
Some phones support a self-destruct feature that will wipe the contents when a passcode is incorrectly entered a number of times. Be absolutely sure you want to do this before activating it, because if one of your mates is on a wind-up and attempting to break into your phone then you could lose everything. Be sure to back up your iPhone or back up your Android phone first.
As a word of warning, using the phone's built-in fingerprint- or iris scanner (assuming there is one) won't stop hackers getting in. Upon the phone failing to recognise the fingerprint or eye scan it will still ask for that failsafe passcode, meaning your phone's security is only ever as strong as your passcode.