I recently had Zone Alarm on my computer and one of its updates stopped me from being able to access the Internet or email. I removed the software… and they came right up. Can you recommend a free firewall download? – Ken

The primary function of a firewall in the computer world is to limit access to and from other computers that are connected through a network. The Internet is the world’s largest computer network, so a firewall is an essential component to reduce the possibility of an unauthorized person gaining access to your computer via the Internet.

I have always used the ‘nightclub bouncer’ analogy to explain firewalls. Think of a firewall as a ‘bouncer’ at the door of your personal nightclub (computer). Only those that are authorized (have an invitation) are allowed to pass by the bouncer.

A nightclub with no bouncer has no way to ‘filter’ patrons as they come in, which makes it less ’secure.’

A big mistake that will compromise the security of your nightclub (and computer) is leaving a back door open (the computer equivalent of opening file attachments that are infected), which will circumvent the security at the front door.

Unauthorized patrons can sneak in the back door and once they are inside, they can alert other unauthorized patrons on how to access the ‘back door.’

A common misconception surrounding firewalls is that they somehow prevent viruses and other malicious code from attacking your computer… nothing could be further from the truth.

Most malicious code generally comes to you as an attachment in email or text message or by visiting a Web site that attempts to silently download its malicious code (aka drive-by downloads). Once an infected file is opened or a drive-by download is executed it can completely compromise the security created by the firewall.

There are two general types of firewalls; hardware and software-based.

In general, hardware firewalls are easier to install, manage and protect a large number of computers in home or business networks all at once.

If you installed a "broadband router" which allows you to share your high-speed Internet connection with several computers, you have also installed a hardware firewall, which could be all you need if you are a conscientious Internet user.

Even if you only have one computer connected to a high-speed connection, such as a cable modem or DSL, I would highly recommend that you install a broadband router.

Software firewalls can add a second layer of protection, not so much from those that are trying to get in but as a way to alert you whenever a program is trying to access the Internet.

When your computer get’s infected by spyware, adware or identity stealing key loggers, they all try to "phone home" via your Internet connection.

A software firewall will alert you to the fact that a program is trying to access the Internet and block it until you give that program permission to do so.

For those with a technical background, this additional action is fine, but for most average users, this additional level of coverage causes a lot of heartburn (as in your case).

The heartburn comes from not knowing the difference between a valid program (such as your anti-virus, anti-spyware or other security programs) and a rogue program or in your case, how to tell the firewall which programs have permission to access the Internet.

When you first install a software firewall (or if an update resets your permissions), it will stop every access and ask your permission, which tends to drive non-technical folks up a wall.

Another issue to consider is what you do on your local network. If you need to be able to access files and drives from one computer to another on your own network, a software firewall installed on each machine can make that access more complex.

The technically astute crowd doesn’t give the Windows Firewall much credit, because in the past it did little to block outbound traffic. The latest version does a much better job and should be available in any computer that has all the current updates installed (open the Control Panel and then the Security Center to see if it is turned on).

Ken Colburn
President of Data Doctors Computer Services, Host of the award-winning Computer Corner radio show, and Author of Computer Q&A in the East Valley Tribune newspapers.