Apple has revealed more details about its new feature for automatically locking a phone that detects it has been snatched by a thief. The complexity of the system shows what a difficult balance it involves.

The big goal is to make sure that if somebody grabs a phone from somebody's hands (for example, when riding past on a bike), they can't take advantage of it being unlocked because it was being used. The problem is how to achieve that without false positives triggering it so often it becomes deeply annoying and users want to switch the feature off.

Weighing the Signals

Apple's solution is to not rely on a single trigger such as the phone suddenly moving. Instead, it combines multiple factors and weighs up the information each is giving. This means the lock won't necessarily be instant: with some combinations, it could be a short time before the system is confident enough to lock the phone. That's a clear indication of the compromise and balance involved as this certainly isn't ideal with a genuine theft. (Source: softonic.com)

Code in a beta version of the next major iOS update shows at least five signals which the system will use. They include the device's movement (specifically acceleration); losing connection to a paired device such as an Apple Watch; continuing to be out of range of the paired device; losing connection to a network (eg WiFi) for an extended time; and the phone being unlocked for an unusually long time. (Source: 9to5mac.com)

Preventing False Alarms

To reduce the annoyance of false positives, the feature appears to tweak how quick and easy it is to unlock the phone again with a biometric check such as fingerprint or facial recognition. If the auto lock triggers repeatedly in a short period and the phone is unlocked every time (showing a false positive), it will be temporarily disabled.

There will also be some use of mitigating factors. For example, the feature may be less likely to trigger if the phone is in a location where it is often used. That would suggest it's a home or workplace, where the phone being snatched is much less likely.

What's Your Opinion?

Have you ever had your phone snatched while using it? Do you think false positives will make this feature too annoying to keep enabled? What other security measures would you like to see smartphone makers implement?