https://www.theverge.com/2018/7/9/17549538/apple-ios-11-4-1-blocks-police-passcode-cracking-tools

Apple today released iOS 11.4.1, and while most of us are already looking ahead to all the new stuff coming in iOS 12, this small update contains an important new security feature: USB Restricted Mode. Apple has added protections against the USB devices being used by law enforcement and private companies that connect over Lightning to crack an iPhone’s passcode and evade Apple’s usual encryption safeguards.

If you go to Settings and check under Face ID (or Touch ID) & Passcode, you’ll see a new toggle for USB Accessories. By default, the switch is off. This means that once your iPhone or iPad has been locked for over an hour straight, iOS will no longer allow USB accessories to connect to the device — shutting out cracking tools like GrayKey as a result. If you’ve got accessories that you want to continue working after your iPhone has been sitting locked for awhile, you can toggle the option on to remove the hour limit.