What is Lockdown Mode on iPhone and how do you enable it?

Apple's Lockdown Mode for iPhone is getting significant attention this week.

On Wednesday, 404 Media reported the FBI has so far been unable to access the seized iPhone of a Washington Post reporter during an investigation. The barrier to entry? The publisher reports the phone has Lockdown Mode enabled, a feature Apple added in 2022 as heavy personal defense against sophisticated cyber attacks.

Added by Apple with iOS 16, Lockdown Mode was launched as "an extreme, optional protection...