(Pocket-lint) - Apple has quietly rolled out a major security feature to iPhone and iPad.

Called USB Restricted Mode, the feature prevents USB accessories from connecting to an iOS device if the device has been locked for more than an hour. This should make it harder for law enforcement to crack your passcode. It’s also thought that USB Restricted Mode is Apple’s way of halting devices, like GrayKey, that are meant to crack an iOS device’s passcode and retrieve data normally protected by encryption. 

Here's how USB Restricted Mode works.

What is USB Restricted Mode?

Apple pushed out the iOS 11.4.1 update out on 9 July, and with it, it released a feature called USB Restricted Mode. This feature is supposed to make it more difficult for hackers - as well as law enforcement and government agencies - to unlock your iPhone. Apple described it as a new “security protection” meant to bulk up existing iOS security features that prevent constant passcode guesses.

For instance, iOS will lock down your device after several incorrect passcode attempts. But law enforcement and some companies have figured out a workaround via USB accessories and the Lightning port. Now, Apple is stopping that way of gaining entry to an iOS device.

How does USB Restricted Mode work?

After an hour of your iPhone, iPad, or iPod Touch sitting idle without being unlocked, iOS will cut off the Lightning port and limit it to charging only - as long as USB Restricted Mode is enabled. This should theoretically prevent devices like GrayKey, which can plug into an iPhone and crack the passcode within a few hours. Here's Apple’s support page if you want more information on the new security feature.


How to enable or disable USB Restrict Mode

Once you’ve installed iOS 11.4.1, Apple automatically turns on USB Restricted Mode. If you'd like to find the toggle to switch it on or off, tap on Settings > Touch ID (or Face ID) and Passcode. Enter your passcode, and then scroll down until you reach USB Accessories. Toggle this option to green if you want to turn it off (your USB accessories will then function the way they did before iOS 11.4.1).

Can you still use your USB accessories?

Yes, just unlock your iPhone or iPad. That'll tell the software it's OK for you to connect a USB accessory, and for as long as it’s attached, the accessory will remain connected - even if your iOS device is locked again. Here's how Apple explains it:

"If you don’t first unlock your password-protected iOS device - or you haven’t unlocked and connected it to a USB accessory within the past hour - your iOS device won’t communicate with the accessory or computer, and in some cases, it might not charge. You might also see an alert asking you to unlock your device to use accessories."

For more iOS tips and tricks, see our guides:

Writing by Maggie Tillman.