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What is USB Restricted Mode in macOS Ventura, and why do you want it?


Once upon a time, one attack vector for industrial sabotage consisted of exfiltrating data from Macs using a standard-issue USB storage card. Researchers have also shown that it’s possible to hijack computers with malware-infested cables. It’s a jungle out there, so Apple has toughened up (Apple Silicon) Mac protection with USB Restricted Mode.

What is USB Restricted Mode?

Beginning with macOS Ventura, the new layer of protection comes in the form of USB Restricted mode, which should provide a little reassurance to enterprise IT and is enabled by default.

An Apple developer note explains this protection: “On portable Mac computers with Apple silicon, new USB and Thunderbolt accessories require user approval before the accessory can communicate with macOS for connections wired directly to the USB-C port.”

If this sounds familiar, it is. It already exists on iPads and iPhones. It’s worth noting that support for mass storage devices on both those platforms always lagged the Mac, and it’s only since iOS 13 that you have been able to use external storage with those.

On the Mac, things have kind of worked in the other direction. Macs have always supported external storage media, but Apple has now made this more secure — though Apple Silicon systems.

How USB Restricted Mode works

The idea is that when a new USB or Thunderbolt device is connected to the Mac, the user will be asked to approve the connection. If a Mac is locked the end user must unlock it before the computer will recognize the accessory. This uses the new-to-the-Mac allowUSBRestrictedMode restriction. The protection is initiated when your Mac has been left locked for an hour or so.

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