(Take Xiaomi Android system as an example)
1. First turn on the phone, find "Settings", and then click on it.
2. After entering the settings, slide the screen and find "Other Settings".
3. In other settings, click Security and Privacy.
4. We turn off the "Allow the installation of applications from unknown sources" switch, so that the mobile phone will not automatically install applications.
The above is my operation, I hope it will help you.