iOS 18.1 will reboot iPhones to a locked state after 72 hours of inactivity

In recent weeks, law enforcement in the United States discovered, to their dismay, that iPhones were automatically rebooting themselves after a few days of inactivity, thereby denying them access to the contents of these phones. After a lot of speculation online, Jiska Classen dove into this story to find out what was going on, and through reverse-engineering they discovered that this was a new security feature built by Apple as part of iOS 18.1, to further make stolen iPhones useless for both thieves as well as law enforcement officers.

It’s a rather clever feature. The Secure Enclave Processor inside the iPhone keeps track of when the phone was last unlocked, and if that period exceeds 72 hours, the SEP will inform a kernel module. This kernel module will then, in turn, tell the phone to gracefully reboot, meaning no data is lost in this process. If the phone for whatever reason does not reboot and remains powered on, the module will assume the phone’s been tampered with somehow and kernel-panic. Interestingly, if the reboot takes place properly, an analytics report stating how long the phone was not unlocked will be sent to Apple.

The reason this is such a powerful feature is that a locked iPhone is entirely useless to anyone who doesn’t have the right code or biometrics to unlock it. Everything on the device is encrypted, and only properly unlocking it will decrypt the phone’s contents; in fact, a locked phone can’t even join a Wi-Fi network, because the stored passwords are encrypted (and I’m assuming that a locked phone does not provide access to any methods of joining an open network either). When you have a SIM card without any pincode, the iPhone will connect to the cellular network, but any notifications or calls coming in will effectively be empty, since incoming phone numbers can’t be linked to any of the still-encrypted contacts, and while the phone can tell it’s received notifications, it can’t show you any of their contents.

A thief who’s now holding this phone can’t do much with it if it locks itself like this after a few days, and law enforcement won’t be able to access the phone either. This is a big deal in places where arrests based purely on skin colour or ethnicity or whatever are common, like in the United States (and in Europe too, just to a far lesser degree), or in places where people have to fear the authorities for other reasons, like in totalitarian dictatorships like Russia, China or Iran, where any hint of dissent can end you in harsh prisons.

Apple is always at the forefront with features such as these, with Google and Android drunkenly stumbling into the open door a year later with copies that take ages to propagate through the Android user base. I’m legitimately thankful for Apple raising awareness of the need of features such as these – even if they’re too cowardly to enable them in places like China – as it’s quite clear a lot more people need to start caring about these things, with recent developments and all.