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Firewall Protection for Mac OS X

Mac OS X includes a firewall: a security measure that protects your computer from connections initiated by other computers when connected to a network or the Internet.

To Turn on the Firewall

Mac OS 10.5

1. From the Apple menu, choose System Preferences.
2. Select Security in the Personal row.
   
3. In the Security window, click on the Firewall tab.
4. Select Set access for specific services and applications.
   The top section of the window lists any running network services. These are set automatically based on any services you turned on in the Sharing preferences pane. Below that you will see applications you have authorized to accept or deny incoming connections. When you launch an application for the first time, you will be asked if you want to allow it or block it. The application is then added to the list.
   

Advanced Firewall Settings (10.5)

You can add a few more layers of security by using the Advanced feature.

1. In the Security window of System Preferences, click on the Advanced button in the Firewall pane. (See above)
2. Check Enable Firewall Logging.
   This will keep track of all connections to your Mac and allow you to see what machines tried to connect and which ones were denied.
3. Check Enable Stealth Mode.
   This will hide the fact that your machine even exists from unauthorized machines.
4. Click the OK button.

Mac OS 10.4 and earlier

1. From the Apple menu, choose System Preferences.
   
2. From the Internet & Network pane, choose Sharing.
3. Click on the Firewall tab.
4. Click Start.
   

Advanced Firewall Settings (10.4 - Tiger Only)

You can add a few more layers of security by using the Advanced feature.

1. Click on the Advanced button in the Firewall pane of the System Preferences. (See image above.)
2. Check Block UDP Traffic.
   This is a low level messaging protocol that isn't as secure as others.
3. Check Enable Firewall Logging.
   This will keep track of all connections to your Mac and allow you to see what machines tried to connect and which ones were denied.
4. Check Enable Stealth Mode.
   This will hide the fact that your machine even exists from unauthorized machines.
5. Click OK.

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