There was much talk recently about a bug in the newer iOS firmware that allowed an attacked to brute force as many passcodes as possible on the phone untill he got the right passcode (it got patched in the newer releases).
More about it here: https://www.reddit.com/r/ios/comments/6ugkoi/this_500_device_can_hack_iphone_7_and_iphone_7/
Also there is another method by the name "NAND Mirroring" which as far as I know was used for the San Bernardino iPhone.
More about it here: https://www.zdziarski.com/blog/?p=6015
My question is why hasn't anyone made a tool to emulate iOS yet?
An iOS emulator would allow an attacker to make the bruteforcing procedure a lot faster.