Apple’s Lockdown Mode

by Bruce Schneier on July 26, 2022

I haven’t written about Apple’s Lockdown Mode yet, mostly because I haven’t delved into the details. This is how Apple describes it:

Lockdown Mode offers an extreme, optional level of security for the very few users who, because of who they are or what they do, may be personally targeted by some of the most sophisticated digital threats, such as those from NSO Group and other private companies developing state-sponsored mercenary spyware. Turning on Lockdown Mode in iOS 16, iPadOS 16, and macOS Ventura further hardens device defenses and strictly limits certain functionalities, sharply reducing the attack surface that potentially could be exploited by highly targeted mercenary spyware.

At launch, Lockdown Mode includes the following protections:

Messages: Most message attachment types other than images are blocked. Some features, like link previews, are disabled.
Web browsing: Certain complex web technologies, like just-in-time (JIT) JavaScript compilation, are disabled unless the user excludes a trusted site from Lockdown Mode.
Apple services: Incoming invitations and service requests, including FaceTime calls, are blocked if the user has not previously sent the initiator a call or request.
Wired connections with a computer or accessory are blocked when iPhone is locked.
Configuration profiles cannot be installed, and the device cannot enroll into mobile device management (MDM), while Lockdown Mode is turned on.

What Apple has done here is really interesting. It’s common to trade security off for usability, and the results of that are all over Apple’s operating systems—and everywhere else on the Internet. What they’re doing with Lockdown Mode is the reverse: they’re trading usability for security. The result is a user experience with fewer features, but a much smaller attack surface. And they aren’t just removing random features; they’re removing features that are common attack vectors.

There aren’t a lot of people who need Lockdown Mode, but it’s an excellent option for those who do.

News article.

EDITED TO ADD (7/31): An analysis of the effect of Lockdown Mode on Safari.