What is a Firewall and Why is it important?

If you have been using the Internet for any length of time, and especially if you work at a larger company and browse the Web while you are at work, you have probably heard the term firewall used. Basically, a firewall is a barrier unauthorized Internet users from accessing private networks connected to the Internet, especially intranets.

The term “firewall” originally means a fireproof wall intended to prevent the spread of fire from one room or area of a building to another. A firewall’s purpose is very simple: to block or filter people from accessing your computer remotely or viruses and worms infecting your machine. Its basic task is to regulate some of the flow of traffic between computer networks of different trust levels. Some firewalls will also monitor outgoing traffic for suspicious behavior. One characteristic of many viruses is that once you’re infected they attempt to establish connections to other computers to spread.

Firewalls are also used to limit the access of individuals on the internal network to services on the internet along with keeping track of what is done through the firewall. A firewall is considered a first line of defense in protecting private information.

All messages entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet the specified security criteria. Firewalls operate in two ways, by either denying or accepting all messages based on a list of designated acceptable or unacceptable sources or by allowing or denying all messages based on a list of designated acceptable or unacceptable destination ports.