USB Restricted Mode has officially made it onto an officially circulating iOS build as iOS 11.4.1. The main intent of the setting is to prevent USB-based accessories from interacting with an iPad or iPhone after the device has been locked for more than one hour.
Law enforcement agencies have been using hacker box products that connect to an Apple mobile device held in evidence to unlock it without triggering the native data erasure feature on iOS after ten wrong passcode attempts. Restricted Mode would prevent police from using the tools. It was thought for a moment that Restricted Mode could be penetrate with brute force by manipulating constant input into the passcode entry field, but that theory has been put down.
USB Restricted Mode is on by default. However, if users want to disable the mode — say, to allow them to control an iPhone connected to an audio dock with a remote control without having to touch the device after an hour — they can head to the security settings and turn on the toggle for “USB Accessories.”