Firewall No Root
Firewall No Root uses artificial intelligence to block spy servers automatically on detection.
When getting started with it, you get a choice to select a default startup option:
Silent mode allows all connections, and you can block individual connections as required (the recommended setting for beginners).
Warn mode is for checking which apps are silently connecting to an unsecured server. After selecting warn mode, the firewall will block all apps and services from connecting to the internet. You have to manually allow apps from the quick settings panel or in the app.