Hidden feature in iOS 18.1 reboots iPhones automatically, making them more secure and thwarting police

A hidden feature baked into iOS 18.1 makes iPhones so secure that even law enforcement is unable to break into them.

Dubbed "inactivity reboot," the feature (which was not advertised in the update and is not available to end users) automatically reboots an iPhone (like the iPhone 16 Pro Max, available at Amazon) after it has been inactive for four days. This pushes the iPhone into a state known as "Before First Unlock," or BFU. When in the state, the iPhone can only be unlocked by entering the users numerical passcode. 

If an iPhone has been unlocked after rebooting, known as "After First Unlock" or AFU mode, it is more vulnerable to attacks or tools that can be used to unlock it. For example, bad actors can use exploits or tools to get into an iPhone in AFU mode, and law enforcement can force the owner of an iPhone to unlock the device with biometric methods like Touch ID or Face ID.

In BFU mode, though, these methods are unavailable. The phone can only be unlocked by using the registered PIN, which is protected under U.S. law. In other words, law enforcement officers cannot compel a user to input a PIN to unlock a phone. 

Inactivity reboot appears to be a security method intended to deter thieves from accessing and unlocking or hacking a stolen iPhone, though the feature caught headlines due to law enforcement officers reporting issues with accessing certain iPhones that had been seized as evidence. The feature was confirmed by intrepid software engineers who dug into the iPhone's kernel and found code describing it.

It seems that Apple is steadily improving iPhone security in ways that safeguard user privacy, though they aren't broadcasting it.