New lines of code could be to blame
At the end of last week, a report from 404 Media was published, based on a memo from law enforcement officers in the USA.
According to the report, the police are having problems with iPhones running iOS 18: they switch off uncontrollably and require the corresponding passcode after restarting, which makes it considerably more difficult for the authorities to access the data on the device.
Based on these reports, the developer scene spent the past weekend looking for confirmation or an explanation for this phenomenon and ended up finding something.
Jiska Classen, an engineer at the Hasso Plattner Institute in Potsdam, Germany, explained the differences between iOS 18 and iOS 18.1 in a post on X/Twitter. It seems iOS 18.1 contains new lines of code with the “Inactivity Reboot” function.
Essentially, this means that a system timer switches on every time the iPhone is locked. If the iPhone is not unlocked for a certain period of time – the researchers assume four days, i.e. 96 hours – the iPhone restarts and asks for the current passcode to be entered. The restart after inactivity is apparently only linked to the time of the last unlocking, not to any other circumstances such as connection to nearby devices.
It has not yet been clarified whether the earlier report from 404 Media and the code found in iOS 18.1 are related; it may simply be a coincidence of timing.
Apple is yet to provide an explanation
Apart from that, we would have liked Apple not to hide such functions from its users and hope that nobody would find out about the change. After all, this is a basic function of the iPhone and users can assume a defect if they notice that their iPhone seems to switch off sporadically.
As to the question of whether anyone leaves their iPhone unused for more than four days, there are enough company iPhones in circulation that are only used for business communication on weekdays, a four-day break is not unusual even on the many long weekends, let alone holidays.
