On Android there a gotchya - google play services is capable of acting as a transparent proxy so remember you MUST also disables google services framework / pl

On Android there a gotchya - google play services is capable of acting as a transparent proxy so remember you MUST also disables google services framework / play services internet access to truly block some apps from using the web (I learned this when a webcam app 'icsee' bypassed the VPN firewall by using play services proxy network access. There is a bug in older android which allows data to leak past the VPN while the device is starting and if you disable/enable the VPN connection mid connection. Facebook appears to have a caching component as it will send a large databurst when it's connection is restored. Here's a typical article but the reason firewall isn't standard is you won't get ads and that juicy data stream stops. You will find some apps punish you for restrictions to their internet - learn which ones and uninstall them. https://www.airdroid.com/mdm/android-firewall-settings/ https://www.airdroid.com/mdm/android-firewall-settings/