NetGuard is an open-source app to block Internet access for any app installed on your device. With it you can lower your data usage, save battery life, and of course protect your privacy.
The main window shows a comprehensive list of all the apps installed on your device. Just tap one of the apps to instantly view its upload and download rates. If you're unhappy with the values, all you have to do is block its Internet access. The app supports IPv4/IPv6 and TCP/UDP. It also supports tethering.
NetGuard is a very useful app thanks to which you can easily block Internet access for any app. In the setup options you can also activate interesting features, like getting a notification every time an app tries to connect to the Internet or applying special measures for when you're connected to a certain WiFi network.