How Firewalls Work

This probably should be a blog post rather than on the Wiki.

title: Firewall - Blocking computers

Original date: 2008/05/15 09:53

tags: linux, operating system, draft

description: Info on Firewalls.

If you've seen my article on How computers talk to each other (originally http://tim.tbruce.com/node/47 and now http://www.tbruce.com/posts/how_computers_talk.html), you already have some background. If you haven't read that yet, please read that now.

Since computers require a port to talk to as well as an address, a firewall can do a variety of things to prevent the communication from occurring:

It can set it on (or off)
It can block it
It can look at the data being sent and make a decision to block or send it on
It can look at other information in the packet being transmitted and make a decision