Proxies and Packet Filters in Plain English

The term firewall, in computer jargon, has the same connotation as it would in relation to your house or car. It provides protection against anything that has the ability to destroy your property. In relation to your car and house it protects against fires and in networking it provides protection against attacks on your network or computer. Network firewalls can serve several purposes. They act as a gateway providing access for your network to multiple networks or to the Internet. They can also block traffic flowing to and from the network. They have the ability to choose what is and what is not allowed to flow in and out of the network. The firewall's ability to decide what is and what is not allowed are configurations that are setup by the system administrator as policies or rules. These policies define what traffic the firewall will or will not allow to enter the network. They also define what is allowed to or not allowed to leave the network. These policies are the heart of a firewall.