Setup Mac OS X Firewall

Article, Intermediate, Mac OS X, Security, System Preferences | May 1st, 2008

For those of you who don’t know, Mac OS X comes with a built-in easy to use firewall. This is great for people who are concerned about their security, but don’t want to spend to much money on third party hardware such as routers. This tutorial will help you setup your firewall to protect you from unwanted incoming traffic, but allow you to use your Mac with ease

This tutorial is done using Mac OS X 10.5 Leopard, however 10.4 Tiger is much the same and can be found under the Sharing section of System Preferences.

For the sake of this tutorial we will assume that your computer is connected directly to the Internet and there are no routers or hardware firewalls.

1. Open System Preferences and left click on the Security icon.
2. Left click on the Firewall tab. You’ll notice 3 different bullets to select from. “Allow all incoming connections” will allow any traffic that requests access to your computer in, this is the most open setting. This is the default mode for Leopard. “Allow only essential services” will only allow a few specific system services to be accessed by incoming connections. This will great limit the use of services such as e-mail.
3. The option we want to select is “Set access for specific services and applications.” This will provide us with the most amount of security and flexibility. Select this bullet and click on the + button near the bottom of the window.
4. Select the Applications you want to allow or deny access to. To select multiple Applications at once hold the Command button (beside the spacebar) while you left click on the Application. Click the Add button once your ready.
5. Now specify whether you want to allow or deny access for your Application. Do this for each Application you add to the list.
6. Once your done, test out each of the applications on your list and make sure it’s doing what you specified. Keep in mind for the future, if you have any issues with one of these applications accessing the Internet you can always check out the Firewall Log located under the “Advanced…” button and apply the appropriate action to debug the issue.

You should now have your Firewall setup to your liking. Should you add new Applications that access the Internet, remember to add the appropriate actions for your Firewall. If you find that the Firewall isn’t working smoothly with your set of Applications, you can always return it to the default setting which is to “Allow all incoming connections”.