Bin a wile since i looked in to it and i do use mint on my laptop,sadly i like firewalls and most of the GUI/firewalls for Linux don't do it for me.
One i like for windows "works on all version from 95~xp" is Filseclab, its opensorce too, to bad no-one ported it to Linux.
not a good firewall by it self mind you, if it crashes it doesn't lock the network so sadly i don't use it by it self but in combo with other firewalls in windows and stack em back to back.
Found Vuurmuur firewall, that one looks decent but i haven't tested it yet,graphics for it look like it came from DOS 6.22 command line years lol sad.
Don't know if its for Linux distros though or a standalone Os.
Things like firestarter, UFW do little for me and im talking about GUI for Linux desktop distros, not standalone edge-firewall linux Os, really sad in a way, blackhats get backtrack/kali Linux stiles Os and what do the whites get ? jack.
As well any app or program that try's to use any network should be "A" blocked if no rules are setup for it and "B" user should be asked what to do if it happens.
As well anyone know about any Linux distros that fall in the category of cyber defense stile for white hats?
The good side of the force stile and the reverse of what backtack/kali is.