The Firewall Computer

A firewall is a computer. It is placed between your network (the network you want to protect) and the Internet. Sometimes in large organizations, a firewall will sit between two or more internal networks, to prevent access to a network with important or sensitive information.

All data between the Internet and the protected network must go through the firewall. The firewall provides several services based on important information found in this data - services such as access control, authentication, activity logging, and alarm warnings.

The key to all these services lies in the networking information contained in each piece or chunk of data passing through the firewall. These pieces of data are called packets.