How to use USB Restricted Mode on your iPhone or iPad

Judy Cobb
July 11, 2018

Apple has released iOS 11.4.1 which contains USB Restricted Mode.

No doubt it's only a matter of time before security companies either find a way to reactivate the port or devise a different system to access an iPhone - it is, after all, still software. Here's how to enable this feature.

"What we want to see is more granular control over what can and what cannot trigger the USB Restricted Mode". In a blog post he said a $39 device can "fool USB Restricted Mode". Even when one plugs in a new USB accessory that has never been paired with the iPhone, the timer of the USB Restricted Mode will reset itself. So it wouldn't be hard for police officers to seize an iPhone when it's been recently unlocked, and connect it to a Lightning adapter, preventing the USB Restricted Mode from fully activating, he says.

It is to be noted that one can't break the USB Restricted Mode once it is already engaged.

However, ElcomSoft says that merely plugging in almost any device (not just ones that have previously been connected to that phone), such as Apple's Lightning to USB 3 Camera Adapter, will disable the timer. If you've got accessories that you want to continue working after your iPhone has been sitting locked for awhile, you can toggle the option on to remove the hour limit. This can be done by plugging any USB accessory into the iPhone's Lightning port. Additionally, if the Lightning accessory doesn't include a pass-through power port, there's no way to keep the device fueled during transport. When you connect the iPhone to a computer, the two devices exchange cryptographic keys and establish trust.

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Over the past year or so, we've seen more companies develop ways to unlock locked iPhones for law enforcement, and chances are we would've seen more in the future unless Apple took steps to address this issue.

A really interesting tidbit from the ElcomSoft report is that since iOS 11.4, Grayshift's boxes are already weakened significantly. But security researchers note that it's trivially easy to block that lockout with Apple's own accessories.

Apple hasn't commented yet, but we can assume that a patch will be landing soon.

Of course, the exploit requires that the attacker gain physical access to the phone within one hour of the last time it was unlocked, but according to Afonin, this is not much of a problem.

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