Firewall

A firewall is a safety barrier that hides and protects your Mac from the rest of your network and the Internet by stopping unauthorized information from coming into or going out of your Mac. If you work someplace that has a large network and servers, there's a good chance that some type of firewall is already in place protecting your network, proprietary business records, and client projects from attacks over the Internet. Thanks to its Unix core, Mac OS X has a robust firewall built in. All you have to do is turn it on.

1.	Launch System Preferences (choose Apple menu > System Preferences).
2.	Click the Sharing icon.
3.	In the Sharing preference pane, click the Firewall tab (Figure 10.23). Figure 10.23. Tiger's built-in firewall gives you enterprise-level protection from anyone on the Internet that tries to get to the files on your Mac without authorization. In the Firewall pane of the Sharing preference pane, click the Start button to activate it and click the Stop button to turn it off.
4.	In the Firewall pane, click the Start button to turn your firewall on. If the button says Stop, your firewall is already running.

If you want to make your Mac as close to invisible as possible, enable Stealth Mode. Stealth Mode prevents your Mac from responding to any queries from your network or the Internet to see if it is on and working.

1.	While still in the Firewall pane of the Sharing preference pane, click the Advanced button.
2.	In the dialog that drops down, check the Enable Stealth Mode box.
3.	If you aren't using a voice-over-Internet phone system, and if your IT department doesn't object, go ahead and check the Block UDP Traffic box. UDP is a network protocol similar to the TCP part of TCP/IP. If you want to learn more about networking, check out Chapter 6.

Some information needs to come and go from your Mac through the network and Internet; otherwise, you wouldn't be able to connect to file or font servers, use network printers, check your e-mail, or view Web pages. Applications like InDesign, the rest of the Adobe Creative Suite, and QuarkXPress also use your network connection to activate your software license, and Adobe Version Cue relies on your network to keep document versions synchronized between workstations.

What, Me Worry?

Just because you work for an agency that already has a security plan in place, firewalls, and an IT staff that stays on top of the latest Internet-borne threats doesn't mean you don't need to take an active role in protecting your Mac. If you have a portable Mac that you take out of the office, it's not always protected from the evildoers on the Internet that want nothing more than to destroy your life. Also, the more you know about your Mac's security, the less likely you are to unintentionally expose your Mac and your clients' projects to potential disaster.

Unless you work for an agency that specifically tells you not to use your Mac's built-in firewall, turn it on. If you are already protected by another firewall, you are adding an extra layer of protection for yourself. Although a little adventure in your life is fun, this isn't the place for it. You should always do everything you can to protect the client files you work with because if you lose them, you may lose your client as well.

The Allow options below the Start/Stop button show what types of information can pass back and forth through your firewall. Any item with a check by its name can pass through your firewall. For example, if you share an inkjet printer that's connected to your Mac with other designers on your network, there should be a check next to Printer Sharing.

Occasionally you will see dialogs that tell you that your firewall is blocking an application from sending or receiving data. That's a safety precaution protecting you from having information leave your Mac without your permission. If you want to let the application send and receive its information, click the Allow button. If the application is something familiar to you, like FileMaker Pro or Adobe Version Cue, you're probably OK clicking the Allow button. If, however, you don't recognize the application, clicking Allow might not be such a good idea. Ask your IT department or favorite Mac consultant about the applications you are unsure of.

Working with Network Ports

Just as USB and FireWire ports let you connect different types of devices to your Mac, network ports let you connect with different types of information. In reality, network ports are part of the protocols that transfer data over your network and across the Internet, but without them, no data would ever move around.

There are different ports for most every type of information that winds its way through your network. Each port is assigned its own number so that your Mac and other network devices know what type of data is passing through. If the number isn't on your firewall's list of accepted data, it doesn't get through. For example, when you visit a Web page, that information passes through port 80. If port 80 is blocked, your Web browser can't go look for the page you want to view, and the page information can't make it back to your Mac.

Most of the time, you don't need to worry about network ports because your agency's or Mac's built-in firewall will manage them for you. In fact, most applications that need to pass information through network ports that aren't already open in your firewall will ask permission to open up those ports.

If an application fails to ask to open a network port, you may have to create the port yourself. Applications from Adobe and Quark shouldn't require any special network ports. A custom-designed network database or project-management system, however, may be a different story. Before you get started, you'll need to know the port number that you are adding to your firewall. The application documentation should tell you what ports need to be open, but you may have to contact the developer's technical support team to get the information.

Let's assume that you are sharing a FileMaker Pro database that contains client and project information with the other designers in your office. Something goes wrong, and FileMaker doesn't automatically open the network port in your Mac's firewall that it uses to transfer the database information to other users. You check FileMaker's online help and find out that it uses port 5003. Here's what you do:

1.	Launch System Preferences (choose Apple menu > System Preferences).
2.	Click the Sharing icon.
3.	In the Sharing pane, click the Firewall tab.
4.	In the Firewall pane, click the New button.
5.	In the dialog that drops down, choose Other from the Port Name pop-up menu (Figure 10.24). Figure 10.24. The Port Name pop-up menu lists network services that Tiger is familiar with. Choose Other to add something that isn't on the list.
6.	Enter the port number you want to open in the TCP Port Number(s) field. In this case, enter 5003 (Figure 10.25). Figure 10.25. If you choose Other from the Port Name pop-up menu, you have to enter the port number yourself. Don't forget to add a descriptive name in the Description field.
7.	Leave the UDP Port Number(s) field blank.
8.	Enter a name that makes sense to you, like FileMaker Pro, in the Description field.
9.	Click OK to create your new network port.

Tip

If you are using Retrospect to back up your Mac over a network, and the necessary firewall port isn't open, choose Retrospect from the Port Name pop-up menu instead of Other. Retrospect's network port information will fill in automatically.