USB Restricted Mode in iOS 12 version prevents USB accessories from having access to data when your iOS device is locked for more than an hour.
In iOS 12 version, Apple restricts access of USB accessories plugged into the Lightning port if that device they connect to has not been unlocked in one hour. As a result of this change, to connect a USB accessory or plug your device into a Mac or Window PC, you will need to unlock your iPhone, iPad. People who want to sync their devices using iTunes will need to allow USB access when locked.
According to Apple, USB Restricted Mode in iOS 12 can increase the security at the expense of convenience. But the fact is that you could not sync with iTunes without re-authorizing your USB accessory if your phone is locked for one hour since USB Restricted Mode will automatically limit the Lighting port. If you plug USB accessories on your device or connect it to a Mac or Windows PC, you will have to periodically re-authenticate with your passcode, Touch ID or Face ID (on iPhone X).
If you use USB accessories through the Lightning port based on the iPod Accessory Protocol (iAP), you will be asked to unlock before you can allow data connection.
This will affect some types of devices such as Apple Carplay, Assistive devices, Charging accessories and others. The change will prevent a locked device from using an iAP charger.
Restrict USB Restricted Mode
In iOS 11.3 beta version, Apple increased security by requiring re-authentication of any USB devices that are connected through the Lightning port if the device has been locked for a week. The company then removed that feature in the official iOS 11.3 version without any reason.
To defeat physical data access by hacking tools, Apple has already tightened up security in its iOS 12 version by adding USB Restricted Mode to prevent USB accessories from accessing data through the Lightning port in just one hour. It means hacking boxes will not be able to run code on iOS 12 devices after one hour.
How to adjust iPhone USB data access
By default, iOS 12 prevents USB accessories from accessing data to a locked iOS device after one hour until you re-authorize your device. However, you can still adjust this behavior. Here is how to do it:
- Launch Settings app on your iPhone /iPad running iOS 12.
- Depending on the type of biometric features, you can choose Passcode, Touch ID & Passcode or Face ID & Passcode, and then enter your passcode.
- Scroll to the bottom and toggle USB Accessories option:
- If “USB Accessories” is enabled, USB accessories can easily connect to your device without worrying about whether your phone is locked for more than an hour.
- If “USB Accessories” is turned off, USB accessories will not be able to establish a data connection when your device is locked for more than an hour.
USB accessories can easily access data on unlocked devices. If your USB accessory isn’t recognized even when you have unlocked your device, you should disconnect the accessory, unlock your device and then reconnect it to check the result.