New code introduced in the latest version of Apple's mobile operating system could make it more difficult for both police and thieves to unlock iPhones.

Apple’s iPhones employ two main states: Before First Unlock (BFU), which sees information encrypted and Face ID disabled until a user enters a passcode after a reboot. Then there’s After First Unlock (AFU), which is easier to crack when law enforcement needs to and offers more data on the display screen.

Multiple iPhone units stored for forensic analysis have rebooted themselves, causing concern among law enforcement officials that Apple has a new security feature.