OS X Lion: Protect your computer with a firewall

Mac OS X includes a personal firewall that can be used to block unwanted incoming connections to your computer. A firewall protects the services on your computer from other computers on networks or the Internet.

Services that were turned on in Sharing preferences already appear in the list. To prevent incoming connections from one of these services, you must turn off the service in Sharing preferences. For more information about sharing, read the help topic:

Share your computer with others on your network

You can’t edit the firewall ports used by built-in services. They are enabled and disabled automatically when you turn the corresponding service on or off in the Services pane of Sharing preferences.

1. Choose Apple menu > System Preferences, click Security & Privacy, and then click Firewall.
2. Click the lock icon to unlock it, and then type an administrator name and password.
3. Click Start to turn on Firewall.

1. Choose Apple menu > System Preferences, click Security & Privacy, and then click Firewall.
2. Click Advanced.
3. Click Add (+), and then select the application or service in the dialog that appears.

1. Choose Apple menu > System Preferences, click Security & Privacy, and then click Firewall.
2. Click Advanced.
3. Select the “Block all incoming connections” checkbox.

1. Choose Apple menu > System Preferences, click Security & Privacy, and then click Firewall.
2. Click Advanced.
3. Select the “Automatically allow signed software to receive incoming connections” checkbox.