Network Firewall

What is a firewall?

A network firewall is designed to limit access to a computer or network. There are a variety of reasons you would want to do this, but all of them revolve around the idea of limiting who has access to a given resource.

Why do I need a firewall?

A firewall can complement Antivirus software in helping to protect your computer. While no software can completely prevent any attack against your computer a firewall can provide another level of defense against attackers.

Why should I care? I don't have anything on my computer that an attacker would want.

First of all ask yourself a few simple questions:

1. Do I use my computer for online banking?
2. Do I use any kind of financial management programs on my computer?
3. Do I use my computer to buy things online?

If you answered yes to any of the questions, then you definately do have something of value on your computer. A large number of recent attacks have invovled harvesting online banking information or credit card numbers.

I don't use my computer for anything other than working on papers, e-mail, and games. Do I still need to worry about all of this?

YES! Even if you do not use your computer for anything other than simple tasks, your computer still has resources on it that many attackers want access to, namely CPU cycles and an internet connection. Current estimates suggest that well over half of the junk e-mail that is sent originates off of home computers. The vast majority of these computers have been infected by various worms and viruses and are spewing out SPAM without the owners knowdlege or consent. This means that by ignoring security warnings you may actually be contibuting to the SPAM problem. Don't think it can happen to you? It can. In the past couple years we have seen multiple cases of Pomona College student computers being infected with viruses and sending out large amounts of spam.

How do I install and configure a firewall?

All current operating systems include firewall capabilities. The specifics of how you enable and configure your firewall vary by operating system.

Windows XP

The firewall that is included in Windows XP versions prior to Service Pack 2 is very unfriendly to users who do not have an intimate knowledge of networking. Thus the first step in configuring your firewall on Windows XP should be to upgrade to Service Pack 2. Once you have done that the firewall will be automatically enabled.

By default the firewall is configured to block most attempts to connect to your computer. Depending on what you do with your computer you may wish to allow other services, like Remote Desktop, File & Printer Sharing, games, etc. Generally when the firewall blocks a program it will give you a dialog box to allow you to unblock the program. If you see a prompt like this, you should examine it and determine if you think that program should be able to recieve connections from other computers.

If you need to manually adjust the settings you can reach the firewall settings by opening the control panel and selecting Security Center. You should see a window popup that contains some basic security information.

If you select Windows Firewall you should get a new windows that will allow you to configure your firewall settings.

Mac OS X

To set up the firewall in Mac OS X, open System Preferences and click on Sharing in the Internet & Network section.

On the Services tab, you should not need any of the choices selected. If you wish to share files or folders, then you should select Windows Sharing.

On the Firewall tab if you scroll down the list, you should select iTunes Music Sharing if you want to share music in your iTunes library. You will also need to turn on Sharing in iTunes under iTunes Preferences.

To turn on the Firewall, click on the Start button beneath the three tabs. If the Firewall is already on, then you will see Firewall On above the button, which will now be named Stop.