Firewalls

A firewall is a blockade between a secure internal network and an untrusted network such as the Internet.

Most companies use a firewall to connect an internal network safely to the Internet, although you can also use a firewall to secure one internal network from another.

A firewall provides a controlled single point of contact (called a chokepoint) between your secure internal network and the untrusted network. The functions of the firewall are as follows:

• Enabling users in your internal network to use authorized resources that are located on the outside network
• Preventing unauthorized users on the outside network from using resources on your internal network

When you use a firewall as your gateway to the Internet (or other networks), you reduce the risk to your internal network. Using a firewall also makes administering network security easier because firewall functions carry out many of your security policy directives.