iOS 18 introduces a new inactivity reboot security feature that protects data on the iPhone by initiating a reboot after 3 days of inactivity. This feature, known as Before First Unlock (BFU), encrypts user data until the passcode is entered for the first time after a restart. In the After First Unlock (AFU) state, user data is decrypted, allowing for more convenience but also making the device more susceptible to attacks. Law enforcement and criminals can take advantage of this state to access valuable information. This feature is not related to wireless activity and is a powerful mitigation against unauthorized access.
https://naehrdine.blogspot.com/2024/11/reverse-engineering-ios-18-inactivity.html