You should note that some spam is going to get through your firewall as long as you accept e-mail. And, while some firewalls offer virus protection, it is worth the investment to install anti-virus software on each computer.

The level of security you establish will determine how many threats can be stopped by your firewall. You can restrict traffic that travels through the firewall so that only certain types of information, such as e-mail, can get through. The highest level of security would be to simply block everything. Obviously, that defeats the purpose of having an Internet connection. But a common rule of thumb is to start out blocking everything, and then begin to select what types of traffic you will allow. This is a good rule for businesses that have an experienced network administrator who understands what the needs are and knows exactly what traffic to allow through. For most of us, it is probably better to work with the defaults provided by the firewall developer unless there is a specific reason to change them.

Windows XP provides a software firewall as part of the operating system. You can activate it from the same dialog you use to activate Internet Connection Sharing (see above).

Hardware firewalls are incredibly secure and not very expensive. One of the best things about a firewall from a security standpoint is that it stops anyone on the outside from logging onto a computer in your private network. For more information on firewalls, see How Firewalls Work.