Like any firewall, you write the correct rules for it! Allow what you want to allow and block what you don't. I was just giving examples, the rules themselves

Like any firewall, you write the correct rules for it! Allow what you want to allow and block what you don't. I was just giving examples, the rules themselves are quite complex, same as with most firewalls but even more so with the variation of good/bad code out there! It's an impossible game. That, however, wasn't my point. My point is a firewall doesn't just have to refer to a network device as the OP (seems to) suggsest.