Some developers have found that the Android 9 Pie introduces a new feature called “Lockdown”. Obviously, Google did not emphasize this feature in its release note but it is very important to protect the privacy of mobile phones.
Specifically, after turning on the “Lockdown” feature, all the core information of your smartphone is encrypted and protected. When you enable this function, press and hold the power button in the lock screen state, you can see this Lockdown feature. It should be noted that when the Lockdown function is enabled on your mobile phone, other people can’t have access to the mobile phone system even through effective fingerprint or face recognition, because the system smart unlocks through your reset PIN code, password or graphic password.
This is a good complement to current biometrics and can even be seen as a last line of defense. The way to turn this feature on is also very simple. Go to Settings, Device Security and click on Lock Screen Preferences, then click on the lockdown option.