How iOS 11.4.1 Stops USB Attacks and Bad Emojis
https://duo.com/decipher/how-ios-1141-stops-usb-attacks-and-bad-emojis [duo.com]
2018-07-13 18:04
Known as USB Restricted Mode, the setting prevents any USB accessory from communicating with an iOS device that hasn’t been unlocked in the past hour. The feature is included in iOS 11.4.1 and it’s designed to prevent attackers or thieves who get physical access to a locked device from being able to dump the phone’s contents to a computer over USB. Restricted Mode is enabled by default.
Also: http://www.willhackforsushi.com/presentations/iOS-USB-Restricted-Mode.pdf