In the networking sense, a firewall is basically any component (software or hardware) that restricts the flow of network traffic.

Some firewalls are notoriously limited in capability, and others are extremely easy to use.

To permit or deny traffic based on which network device is the sender or recipient and what ports are being used, you would use a packet-filtering firewall

The most securely configured firewall in existence will not provide much protection if the underlying network was not designed properly

A screened subnet is the simplest and most common firewall implementation. Most small businesses and homes use this type of firewall

The one-legged demilitarized zone (DMZ) still has the advantage of cost, because you are building a DMZ using only a single firewall.

The true DMZ is generally considered the most secure of firewall architectures. With this design, there is an external and internal firewall. Between the two is sandwiched any Internet accessible devices.

netfilter is the built-in component that performs the firewall logic. iptables is the command-line interface used to configure the netfilter ACLs.

Many GUI interfaces exist with widely varying degrees of functionality and complexity My suggestion here is choose the simplest one that will do what you need it to do. In all likelihood the right one will change for you over time.

SmoothWall sits in a class of its own, due to the fact that...