Microsoft seems to be rethinking quite a bit when it comes to the mobile version of its next OS. A new feature brings changes to how scenarios where the user may enter their PIN wrong multiple times are handled. We aren't positive when this feature was introduced, but it is present in the more recent builds of Windows 10 Mobile, including Build 10166, which was recently released to Insiders last Friday.
In Windows 10 Mobile, when a user enters their PIN code wrong four times, the user will be prompted with a new screen asking them to enter the challenge phrase "A1B2C3." The user is not given another attempt at the passcode until the this challenge phrase is entered, effectively putting a stop any future accidental or purposeful attempts to enter it wrong. If the user were to enter the challenge phrase correctly and proceed to incorrectly enter the wrong PIN once more, the phone will lock and require a restart.
Typically following a string of miss attempts to enter a PIN correctly, most smartphone devices would proceed to disable the device for an exponentially increasing amount of time. This was meant to disable and make it take exponentially longer for thieves to break into your phone. Unfortunately, this could also be the basis for a prank, when a devious friend decides to steal your device and enter your pin wrong on purpose.
The "challenge phrase" method does away with that opportunity to lock users out for extended periods of time while at the same time makes cracking a user's passcode just as frustrating. iOS still relies on the traditional time increasing lockout style while Android has a feature that allows you to type your email address and password to unlock your device if it has been disabled for an extended period of time.
It's worth noting this particular feature was present back in versions of Windows Mobile as far back as 6.0, but was removed in Windows Phone 8/8.1 in favor of the timer method. It is unknown if Microsoft is planning to stick with this or maybe has other plans regarding security for Windows Mobile.