After the mysterious reboots, the devices supposedly enter what is called the Before First Unlock (BFU) state. This makes cracking them to get data about criminal activity much harder.

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.

The lock state of an iPhone determines how easy it is for cops to use third-party tools like Cellebrite to break in and root around. When an iPhone boots after a loss of power, it’s in BFU and much harder to get into. Cops can still brute force their way into the phone, but it’s harder and the data they can extract is limited.

A hidden feature in iOS 18.1 will automatically reboot a locked iPhone when it is asleep but hasn't been unlocked for a while, presumably as a security measure.

Phones held by the police reportedly underwent a large-scale reboot, making data extraction much more challenging.

A new report from 404 Media says that law enforcement officials in Detroit, Michigan believe that iOS 18 includes a “new security feature that tells nearby iPhones to reboot if they have been disconnected from a cellular network for some time.