Like a lot of people I have at least one old pc kicking around in the loft, so I decided to put it to better use than gathering dust and install some linux on it! I have a home network and have never got round to buying a router for it, instead relying on pc to share the internet connection.

Introduction.

What is a firewall?

Just as a building has a firewall and possibly a fire door to try to isolate a fire on one side of the wall, preventing it spreading to the other side, a computer firewall does much the same. However, it's not concerned with fires, but more to the point, unauthorised entry and use. It most commonly, sits between the computer and the Internet, although in complex networks, there can be others within the overall system.