GlassWire - Visualize network activity in detail, get notified when new apps access the network, look out for...
AdBlock - Ad blocker for Chrome, Safari and Opera on desktop and Safari for iOS devices.
TinyWall - Lightweight and non-intrusive firewall
RethinkDNS - 2B+ Android users deserve access to a safer and open Internet.
Little Snitch - Little Snitch is a firewall application that monitors and controls outbound internet traffic.
Blokada - The best ad blocker for Android. Free and open source.