Here is a guide for automatically bruteforcing 4-digit passcodes on iPhone 5 using only a computer and a USB cable (without an MFC Dongle). My device is iPhone5,2 (iPhone 5 Global) iOS 9.2 (FMI OFF), the steps below may work on other 32-bit devices or other iOS versions (see below for tested working devices and iOS versions), but shall not work on any 64-bit devices.
See https://www.reddit.com/r/setupapp/comments/1ha2arg/bruteforce_4digit_passcode_on_iphone_5_ios_9_via/ for discussions.
Updated 10 Jan. 2025:
A more powerful guide for bruteforcing 32-bit devices was released by a reddit user: https://www.reddit.com/r/setupapp/comments/1hw5bfa/bruteforcing_32bit_iphones_ondevice_4_digit_pin/