If someone tries to access your iPhone or iPad by guessing the passcode, it will initially lock them out, increasing each interval with each failed attempt. You can however, set it up so that it fully erases your device after 10 failed attempts.
If you just lose your iPhone somewhere and it falls into wrong hands then they would probably try to guess the passcode. There can be millions of possible combinations but if a computer is used to force the way through then guessing the passcode is possible. Luckily, iOS employs time delays where the device locks itself after too many failed passcode attempts.
For example, if you make 5 failed attempts, your iPhone will lock for 1 minute, 6 attempts will lock it for 5 minutes, 7 will lock it for 15, and anything more than that will lock it for 1 hour.
That might be enough to dissuade casual data thieves, but there’s always a chance that someone could get lucky and guess it with another few guesses, which is why you should try to use a random or hard-to-guess number. Don’t just use something like 1-1-1-1-1-1 or 1-2-3-4-5-6.
This Device Is Set to Self-Destruct
This is where this option comes into the scene to wipe out your iPhone and iPad after 10 failed attempts. This option is off by default but can be turned on.
To do that go to Settings and tap “Touch ID and Passcode”.
Enter your Passcode.
Scroll to the bottom of the Touch ID & Passcode settings and tap on “Erase Data” to enable the self-destruct feature.
It’s advised that you make frequent local backups of your data using iTunes after this is enabled–otherwise, if your phone gets erased, your data will be gone for good. Also, if you’re concerned about somehow forgetting your passcode, then try using a custom alphanumeric code.
It’s probably a good idea that you commit your passcode to memory first before turning on the erase data option, or turn it off temporarily whenever you change your passcode to something else.