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. For example, you often hear people in companies say things like, "I can't use that site because they won't let it through the firewall." If you have a fast Internet connection at home (either a DSL connection or a cable modem), you may have found yourself hearing about firewalls for your home network as well.

Basically, a firewall is a barrier to keep destructive forces away from your property. In fact, that's why it’s called a firewall. Its job is similar to a physical firewall that keeps a fire from spreading from one area to the next. A firewall is simply a program or hardware device that filters the information coming through the Internet connection into your private network or computer system. If an incoming packet of information is flagged by the filters, it is not allowed through.