Recent iPhone reboot spate is actually an unannounced security feature

If you’ve noticed your iPhone has incurred a random reboot since downloading iOS 18.1 last month, you might have been concerned a bug was going around.

While it would have nice if Apple told us first hand, gladly that’s not the case. The phenomenon is apparently a new security feature Apple snuck into the first major iOS 18.1 update.

With the so-called “inactivity reboot” your iPhone may take it upon itself to reboot the handset. However, it only occurs when the phone has been locked and inactive for a long while – 96 hours to be precise. AppleInsider reports the reboots are only timed based upon the last unlock rather than other factors.

The site quotes digital forensics specialist Christopher Vance of Magnet Forensics as saying: “We have identified code within iOS 18 and higher that is an inactivity timer. This timer will cause devices in an AFU state to reboot to a BFU state after a set period of time, which we have also identified.”

AFU means After First Unlock and BFU means Before First Unlock, so the reboot essentially cleans the slate of actively open apps that are available at the time. The overarching idea is to make it more difficult for law enforcement agencies, or other would-be nefarious actors to get into your device.

The report originated from 404 Media, who interviewed John Hopkins University cryptography expert Matthew Green. He says this will prevent thieves from stealing your iPhone and then holding onto it until they figure out how to get into it.

“Remember that the real threat here is not police,” he said. “It’s the kind of people who will steal your iPhone for malign purposes. This feature means that if your phone gets stolen, the thieves can’t nurse it along for months until they develop the tech to crack it.”