Whether you are one of the growing number of computer users with fast, always-on Internet access or you're still using a dial-up connection, you may want to consider implementing a firewall.

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. You use a firewall to protect your home network and family from offensive Web sites and potential hackers. If an incoming packet of information is flagged by the filters, it is not allowed through.
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. There are also personal firewalls

Use a firewall only for network connections that you use to connect directly to the Internet. For example, use a firewall on a single computer that is connected to the Internet directly by using a cable modem, a DSL modem, or a dial-up modem.
If you use the same network connection to connect to both the Internet and a home or office network, use a router or firewall that prevents Internet computers from connecting to the shared resources on the home or office computers.

Do not use a firewall on network connections that you use to connect to your home or office network unless the firewall can be configured to open ports only for your home or office network. If you connect to the Internet by using your home or office network, a firewall can be used only on the computer or the other device, such as a router, that provides the connection to the Internet.

For example, if you connect to the Internet through a network that you manage, and that network uses connection sharing to provide Internet access to multiple computers, you can install or enable a firewall only on the shared Internet connection. If you connect to the Internet through a network that you do not manage, verify that your network administrator is using a firewall.

Note If you use a firewall on all computers on your home or office network you may be not be able to browse (search) for other computers on your home or office network, and you may not be able to share files with other computers on your home or office network. For additional information about this issue, click the following article number to view the article in the Microsoft Knowledge Base: 298804 Internet firewalls can prevent browsing and file sharing Windows XP; Windows Server 2003, Standard Edition; Windows Server 2003, Enterprise Edition If you are running Windows Server 2003, Standard Edition; Windows Server 2003, Enterprise Edition; or any version of Windows XP, you can use the ICF feature. For additional information about how to turn on ICF, click the following article numbers to view the articles in the Microsoft Knowledge Base: 317530 HOW TO: Turn on the Internet Connection Firewall feature in Windows Server 2003 283673 HOW TO: Enable or disable Internet Connection Firewall in Windows XP For additional information about ICF, visit the following Microsoft Web sites: http://www.microsoft.com/technet/prodtechnol/winxppro/proddocs/hnw_enable_firewall.asp http://www.microsoft.com/technet/prodtechnol/windowsserver2003/proddocs/entserver/hnw_UsingICF.asp Other versions of Windows For other versions of Windows, use Basic Firewall (for Windows Server 2003 servers running Routing and Remote Access), Microsoft Internet Security and Acceleration (ISA) Server 2000 (for Windows 2000 or Windows Server 2003), or a third-party hardware or software firewall. For additional information about 3rd party firewall products, visit the following Microsoft Web site: http://www.microsoft.com/security/articles/firewall.asp

The level of security you establish will determine how many threats can be stopped by your firewall. By establishing rules 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. 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

With a software firewall the computer is considered a gateway because it provides the only point of access between your home network and the Internet.
With a hardware firewall, the firewall unit itself is normally the gateway. A good example is the Linksys Cable/DSL router. It has a built-in Ethernet card and hub. Computers in your home network connect to the router, which in turn is connected to either a cable or DSL modem. You configure the router via a Web-based interface that you reach through the browser on your computer. You can then set any filters or additional information.

• Vigor Router Firewall
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• Protecting part of a system
• Testing a Firewall