One Tech Tip: All you need to know about the iPhone's Lockdown Mode

A little known security feature on iPhones is in the spotlight after it stymied efforts by U.S. federal authorities to search devices seized from a reporter.

Apple's Lockdown Mode recently prevented FBI agents from getting into Washington Post reporter Hannah Natanson 's iPhone.

Agents seized the phone, as well as two MacBooks and other electronic devices, when they searched Natanson's home last month as part of an investigation into a Pentagon contractor accused of illegally handling classified information. But the FBI reported that its Computer Analysis Response Team ''could not extract'' data from the iPhone because it was in Lockdown Mode, according to a court filing.

So what is Lockdown Mode? Here's a rundown of how it works and how to use it:

Highest security

Apple says Lockdown Mode is an ''optional, extreme'' protection tool designed to guard against ''extremely rare and highly sophisticated cyberattacks.'' It's not for everyone, but instead for ''very few individuals'' who could be targeted by digital threats because of who they are or what they do.

''Most people will never be targeted by attacks of this nature,'' Apple's support page says.

Can Apple turn it off?

Apple has previously rejected U.S. government requests to build so-called backdoor access for its devices.

In 2016, Apple refused a request by authorities to help bypass lockscreen security for an encrypted iPhone belonging to a shooter who carried out a terrorist attack in San Bernardino, Calif. The company also declined to add an ability to input passcodes electronically, which would make it possible to carry out ''brute force'' attempts to guess the combination using computers.

''It would be wrong to intentionally weaken our products with a government-ordered backdoor,'' Apple said in explaining its decision.

How to turn on Lockdown Mode

On your iPhone, go to Settings, then to the Privacy and Security section, scroll down to the bottom and tap on Lockdown Mode. Enter your passcode — not a facial or fingerprint scan — to activate it. The device will restart and then you'll again have to use your passcode to unlock it. On MacBooks, follow a similar procedure from the System Settings menu.

Apple recommends that you switch it on for all of the company's devices that you own.

Better than biometrics

You might assume that requiring facial or fingerprint recognition to unlock your phone is good enough to protect it from snooping. But experts say passcodes are better than biometrics at protecting your devices from law enforcement, because they could compel you to unlock your device by holding your phone up to your face or forcing you to put your finger on the scanner.

FBI agents told Natanson that they ''could not compel her to provide her passcodes,'' but the warrant they used to execute the search did give them the authority ''to use Natanson's biometrics, such as facial recognition or fingerprints, to open her devices.'' According to a court filing, Natanson said she didn't use biometrics to lock her devices but agents were ultimately able to unlock her MacBook with her finger.

Apple says some apps and features will work differently when Lockdown Mode is on.

Some websites might load slowly or not work properly, and some images and web fonts could be missing because they block ''certain complex web technologies.''

In Messages, most types of attachments are blocked, and links and link previews won't be available. Incoming FaceTime calls are blocked unless it's from a number you've called in the past month.

In Photos, location information is stripped from shared photos and shared albums are removed from the app. Focus mode won't work normally.

There are also tighter restrictions on connecting your phone or computer to unsecure Wi-Fi networks or to other computers and accessories.

The biggest disruption happened when I went to the gym, which involved checking in by scanning a QR code with the phone camera. But the camera wouldn't work in Lockdown Mode. I had to turn it off in order to get in.

Turn it off

Follow the same procedure outlined above that you used to turn on Lockdown Mode. You'll need to enter your passcode and the phone will perform a restart.

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