Update: July, 28th, 2018: I was told Outpost is no more, so in case you wanna know what the current best firewalls are, here is a nice compassion: https://www.comparitech.com/antivirus/best-free-antivirus/
And it’s great! It’s even better than Outpost I think because you do not just allow or disallow traffic by default but you allow the first caused the traffic only at first (so same IP address or data transfer way, e.g.).
If the same prg wants access to the internet again but by doing it a different way, it will warn about this and offer to either allow all actions to the internet or just the momentary caused one and keeping an eye on it to learn what kind of further communication the prg in question does!
Unfortunately the Visual Trace crashes on all PCs I tried, but well, it’s not that bad, not really something that makes me cry! 🙂