Many people think of a firewall as a guard on your network that just works – and in many cases they function without you ever having to explicitly make policies or understand the under-workings. Let’s look at a Microsoft Windows firewall for instance: for the most part these function in the background without you ever having to know the particulars. The odd time you might be prompted to allow an application inbound or outbound; or for the power user, you might be familiar with creating your own policies based on ports, source and destination address. The name Windows ‘Advanced’ Firewall can be a bit misleading as there’s really nothing advanced about it (sorry to pick on you Microsoft). Many of you (who use windows) may not even feel the need to keep the Windows firewall on, because you feel safe running 3rd party software or place your confidence in the onboard firewalls in home routers and such. I would say that you would be smart not to leave these duties to Windows alone as the onboard Windows Firewall is more reminiscent of the systems of yesteryear.
What “is” a firewall in its purest, simplest form: it’s basically a cop that