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OS X Mountain Lion: Prevent unwanted connections with a firewall

Prevent unwanted connections with a firewall

OS X includes a firewall that can block unwanted incoming connections to your computer. A firewall can shield the services on your computer from other computers while you’re on networks or the Internet.

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

Share your Mac 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.

Turn on firewall protection

  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 Turn On Firewall.

Allow only specified apps and services to connect

  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 Firewall Options.
  4. Click Add (+), and then select the app or service in the dialog that appears.

Allow only essential apps and services to connect

  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 Firewall Options.
  4. Select the “Block all incoming connections” checkbox.

Allow signed software to receive incoming connections

  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 Firewall Options.
  4. Select the “Automatically allow signed software to receive incoming connections” checkbox.
Last Modified: Aug 8, 2013
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  • Last Modified: Aug 8, 2013
  • Article: PH11309
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