No, Your iPhone Is Not ‘Mysteriously Rebooting’: Here’s What’s Happening

Recently, there’s been an iPhone rebooting mystery, with some iPhones have been rebooting without warning and—so it was thought—caused nearby handsets to follow suit. But it now seems something else was going on.

The report came from 404media and was picked up by Kate O’Flaherty here on Forbes. It described “iPhones Mysteriously Rebooting Themselves” when police in Detroit, Michigan found that iPhones held for forensic investigation were rebooting, without any interaction from humans.

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Once an iPhone reboots, it’s more difficult to unlock than once it’s been unlocked. This is the difference between the Before First Unlock and After First Unlock (AFU) states. Until this phenomenon was discovered, simply keeping the iPhone turned on would make it more accessible to police. The police seemed to think that these iPhones were sending instructions to other iPhones nearby that they should reboot, too.

The report says, “The document says that three iPhones running iOS 18.0, the latest major iteration of Apple’s operating system, were brought into the lab on October 3. The law enforcement officials’ hypothesis is that “the iPhone devices with iOS 18.0 brought into the lab, if conditions were available, communicated with the other iPhone devices that were powered on in the vault in AFU. That communication sent a signal to devices to reboot after so much time had transpired since device activity or being off network.”

While it’s nice to think that iPhones can talk to each other in this way, to stop them getting lonely, perhaps, it’s probably not that. It’s true that devices can send information, such as Find My data, but this is something different, not least because some of the iPhones were in Airplane mode and one inside a Faraday cage.

While the police have suggested this is a security feature addition for iOS 18, a user on Mastodon has explained things in a different way, saying, “Apple added a feature called “inactivity reboot” in iOS 18.1. This is implemented in keybagd and the AppleSEPKeyStore kernel extension. It seems to have nothing to do with phone/wireless network state. Keystore is used when unlocking the device. So if you don’t unlock your iPhone for a while… it will reboot!”

This makes a lot more sense, though I note that the police were specific that the iPhones they had were running iOS 18, not 18.1.

Another user has a different answer, saying that there was an iPhone reboot bug in iOS 18 which was fixed in iOS 18.1. This reboot issue affected some iPhone 16 Pro and Pro Max users. Rebooting iPhones with iOS 18 fits with what the police said. Apple Insider thinks this is the most likely explanation, though it’s curious that multiple iPhones in a small sample all had the same reboot problem.

Apple hasn’t commented but it seems to me that this could be something simpler than all that: just as you’ll find that a Mac that has been left idle will require a password unlock after a certain time instead of launching from fingerprint or Apple Watch unlock, so it makes sense to me that Apple would want users to re-enter their password after a while. And a neat way to do that would be to reboot the phone.

Whatever the explanation for the iPhone rebooting mystery, I think it’s safe to assume that while the machines may rise up one day, they’re not talking to each other, scheming together or laughing at us behind our backs. Yet.

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