Under normal circumstances, the default configuration of an Android device does not allow applications to install software from outside Play Store. Such configuration is usually done by the device manufacturer.
For example, on devices pre-installed with the Google Play Store or the manufacturer ’s own store, users must also enable certain options if they want to install applications outside the store.
Under normal circumstances, it is not difficult for users to actively install applications outside the store, but installing applications outside the store may also cause potential security issues for users.
So Google decided to upgrade Google Play-based protection: if the account is enabled for Android Advanced Protection, users will be forbidden from installing apps outside the store.
Roman Kirillov, Engineering Manager, Android Security, and Privacy, said:
“Advanced Protection is committed to keeping harmful apps off of enrolled users’ devices. All apps on the Google Play Store undergo rigorous testing, but apps outside of Google Play can potentially pose a risk to users’ devices. As an added protection, we’re now blocking the majority of these non-Play apps from being installed on any devices with a Google Account enrolled in Advanced Protection. You can still install non-Play apps through app stores that were pre-installed by the device manufacturer and through Android Debug Bridge. Any apps that you’ve already installed from sources outside of Google Play will not be removed and can still be updated.”
For users who need it or professional users, Google of course also provides other ways for users to install from outside the store, such as directly deploying through the ADB command line or you can remove the enrolled account from your device or unenroll from Advanced Protection.