If you have an Apple or an Android phone—and you probably do—you have the option of locking your phone using a PIN code. With most of these phones, you can choose a four-digit PIN or a six-digit PIN.

There's nothing particularly difficult about cracking a smartphone's four-digit PIN code. All it takes is a pair of thumbs and enough persistence to try all 10,000 combinations. But hackers hoping to ...

What's safer? Using a numeric PIN code to unlock your Android smartphone or relying on a finger squiggle? Newly-released research suggests that, at least when someone close by could be looking over ...