Hidden iOS 18.1 Feature Automatically Reboots iPhones for Enhanced Security

A previously unannounced feature in iOS 18.1, dubbed "inactivity reboot," automatically reboots iPhones after four days of inactivity. This enhances security by placing the device in a "Before First Unlock" (BFU) state, making it significantly more difficult to access without the user's passcode. The BFU state requires the numerical passcode for unlocking, unlike the "After First Unlock" (AFU) mode, which is vulnerable to exploits and can be unlocked using biometric methods like Face ID or Touch ID (even by law enforcement). In BFU mode, law enforcement cannot compel users to unlock their devices as entering a PIN is protected under U.S. law. While intended to deter theft, the "inactivity reboot" feature has reportedly caused issues for law enforcement attempting to access seized iPhones. The feature's existence was confirmed by software engineers who discovered code referencing it within the iPhone's kernel. This quiet improvement to…