AFWall+ alias Android Firewall+ is a front-end application for the powerful IPTables Linux firewall. It allows you to restrict which applications are permitted to access your data networks. This is the perfect solution if you don't have an unlimited data plan, or just want extend battery life.
Source Code
GitHub Page
Additional Help
FAQ
AFWall+ is licensed under
GNU General Public License v3.0 License
Developers
Umakanthan Chandran (Active) Contact
Kevin Cernekee Contact
Credits
Pragma (Networklog)
Rodrigo Rosauro (DroidWall)
PdtS (Icons)
werewolfdev (Icons)
Material Design Icons (Icons) - shenm233 CHEF-KOCH (AFWall+ Wiki)
Translators

Chinese Simplified | yinfugang, wuwufei, tianchaoren, Beng-tiong @crowdin
Chinese Traditional | shiuan,Beng-tiong @crowdin
Czech | Syk3s,ondra @crowdin
Dutch | DutchWaG @crowdin
French | GermainZ @xda,Looki75 @xda,La_Globule @crowdin
German | CHEF-KOCH,user_99,Gronkdalonka @xda
Greek | mpqo @crowdin
Hungarian | l3s,Hevesi @crowdin
Indonesian | mirulumam @crowdin
Italian | giammatheo, benzo @crowdin
Japanese | nnnn,naofum @crowdin
Polish | tst,eskimos72,Piotr Kowalski @crowdin
Portuguese | lemor2008,ricardovieira @xda
Romanian | mysterys3by-facebook @crowdin, andycris @crowdin
Russian | Kirhe @xda,YaroslavKa78 @crodwin
Slovenian | bungabunga @crowdin
Spanish | spezzino @crowdin
Swedish | CreepyLinguist @crowdin
Turkish | BahadirDemirel, myasa, ozgurahmet95 @crowdin
Ukrainian | andriykopanytsia,igezo @crowdin
Basque | Osoitz @crowdin
Arabic | alruwaile1234,anbaalie @crowdin
Persian | alruwaile1234,ssttehrani,Imanew,Alfr3dQR @crowdin
Serbian(Cyrillic/Latin) | slsimic @crowdin
Vietnamese | softiceup @crowdin
Korean | testxyz009 @crowdin
Asturian | enolp @crowdin

Used 3rd Party Libraries

Android Color Picker | Apache License 2.0
Busybox | GNU GPLv2
IPtables | GNU GPLv2
Libsuperuser | Apache License 2.0
material-dialogs | MIT
Locale Plugin | Apache License 2.0
Root Tools | Apache License 2.0
DBFlow | MIT