What Is a Firewall?

The term "firewall" doesn't actually refer to any one device. A firewall could be either a piece of hardware or software, and more than one type of firewall can be used to provide extra network security.

There are two common types of firewalls:

A firewall can also screen internal traffic on a network, separating different departments or branches of a large company. In some cases, a business will configure a proxy server to block employee access to certain types of Internet content, such as streaming audio or video.

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If your home or business computer uses DSL, a cable modem or some other type of always-on Internet connection, a firewall is extremely important. Some computer crackers make a hobby out of finding and breaking into these types of systems, and an unprotected computer is a sitting target for anyone who happens to guess your system's IP address.

Fortunately, companies such as Symantec and others sell personal firewall software that installs quickly and easily on your computer and protects against intruders. Other firms make gateway routers — hardware that allows more than one computer to share a single Internet connection — that include built-in firewall software. This type of protection is relatively inexpensive, and it's worth every penny you'll pay to keep your computers safe.