Sams Teach Yourself Microsoft Windows XP in 24 Hours

Sams Teach Yourself Microsoft Windows XP in 24 Hours

By Greg Perry

Introducing the Internet Connection Firewall

Hackers are people who utilize online connections to connect remotely to computers and to program computers remotely. Crackers generally have hacking skills, but they often use their skills in a devious, harmful way, perhaps to erase a remote computer's hard disk. Some people don't distinguish between the two groups, especially the media, but the hacking community likes the distinction. Crackers scan the Internet looking for ways to snoop into other computers. Sometimes hackers are malicious and they want to damage files. Other times, they are just curious or they find that accessing another computer through an Internet connection is challenging.

You can limit the danger of others getting access to your files while you're online by setting up a firewall. A firewall is a hardware or software device that monitors your Internet connection looking for unauthorized use. Dial-up users are prone to cracking at times, but due to the nature of always-on connections such as DSL or cable modems, if you have an always-on connection, your risk is even greater than that of dial-up users at becoming a victim of a cracker.

Windows XP comes with a software-based firewall solution called Internet Connection Firewall (ICF). With ICF, you can specify exactly how information is to communicate between your computer or computer network and the outside world through your Internet connection. Your goal should be to allow all users on your computer's side of the Internet connection to access the Internet freely, while blocking what can occur from the other side of the Internet connection.

Setting Up a Firewall Is Not a One-Time Process

Setting up a firewall can be tricky. Some outside access to your computer is needed for you to use many Web sites properly. For example, often a Web site will send your computer a Java program along with a Web page. The Java program allows you to interact with the Web site in a more timely manner than would otherwise be possible. Other kinds of programs can come to your computer through your Internet connection and often, these programs should have access to do what they're intended to do.

ICF is relatively intelligent. As you access Web sites, ICF builds a table. If a Web site attempts to respond in a manner that is more than simple Web pages coming back to your machine, the ICF checks to see if you had been at the sending site and possibly requested information. If so, ICF lets the information come to your computer. If not, ICF blocks the information.

Sometimes, ICF makes an incorrect decision and blocks information that you want. As you use ICF and the Internet more, you will locate trouble spots and be able to grant permission to those sites that should have access to your machine.

The following To Do item explains how to initially set up your Internet Connection Firewall and what things to look for and modify as you continue to use the ICF.

To Do: Using the Windows XP Firewall

  1. Open your Control Panel and select Network and Internet Connections.
  2. Click the link labeled Network Connections.
  3. Right-click your Internet connection icon. The icon will be a dial-up icon if you have a modem, or a high-speed Internet icon if you have a higher-speed Internet access along with a shared Internet connection. Then display the Properties window from the pop-up menu.
  4. Click the Advanced tab. The Internet Connection Firewall window appears.
  5. Click the ICF option to check it.
  6. Click the Settings button to display the customizable firewall settings shown in Figure 12.5 that you can control.
    12fig05.gif

    Figure 12.5 Set up a firewall to protect your online sessions.

  7. Now the real work begins. You must go through the Services listed in the window, as well as the services on the other tabs, checking all the items you normally use. The problem is, many of the settings are advanced and difficult to understand. By their very nature, firewall settings are difficult. For example, you want to allow e-mail to flow freely, back and forth between your computer and others on the Internet. The window in Figure 12.5 shows two e-mail options, Internet Mail Access Protocol Version 3 (IMAP3) and Internet Mail Access Protocol Version 4 (IMAP4). Which conforms to your e-mail system? Your e-mail service will have to let you know.

    Unless you have strong skills in networking and online protocol, you may have to make a few guesses when setting up your firewall for the first time or two and see what happens. This might not be comforting news to you, but the effort is worth your time if you stop attacks on your system. For example, you might want to check all the e-mail options you think will apply to your computer and then check your e-mail for a while to see if e-mail is getting through properly and being sent from you properly. Of course, your e-mail's intended recipients will have to tell you if they are not receiving e-mail that you tell them to expect.

    Many of the options, such as FTP Server, might be unfamiliar to you; in those cases, leave those options unchecked. As you use the Internet, you might find that you have to return to these settings periodically to tweak one or more options for normal Internet use.

Using a firewall adds a layer of protection, but with that protection comes a layer of complexity. Fortunately, in most cases, after you set up your firewall and get it working smoothly, you will have little need to return to the firewall settings unless you add new networking or online hardware in the future or change the way you access the Internet.

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