Most of the time we want our applications online and connected to both our local network and the greater Internet. There are instances, however, when we want to prevent an application from connecting to the Internet. This is where firewall comes into the picture. It helps you block programs and restrict their internet access as per your wish.

Why would you Do This?

Some of you might have been sold immediately by the headline, as blocking an application is exactly what you’ve been wanting to do. Others may have opened this tutorial curious as to why one would block an application in the first place.

Although you generally want your applications to have free access to the network (after all what good is a web browser that can’t reach the web) there are a variety of situations in which you may wish to prevent an application from accessing the network.

Some simple and commonplace examples are as follows. You might have an application that insists on automatically updating itself (but those updates break some functionality and you wish to stop the updates). Also, you might have a video game that you’re comfortable with your child playing, but you’re not so comfortable with the online (and unsupervised) multiplayer elements. You might be using an application with really obnoxious ads that can be silenced by cutting off the application’s Internet access.

Regardless of why you want to drop the cone of network connectivity silence over a given application, a trip into the guts of the Firewall is an easy way to do so. Let’s take a look at how to enable or disable the firewall in Mac OS X.

Mac OS X 10.6 and later

Step 1:

From the Apple menu, select System Preferences. When the System Preferences window appears, from the View menu, select Security & Privacy (10.7 and later) or Security (10.6)

Image result for mac os x firewall

Step 2:

Click on the firewall tab

Step 3:

If the orange padlock icon in the lower left side of the window is closed, click it, and then authenticate with your Mac’s administrator username and password. This will allow you to make changes.

Step 4:

Click Turn On Firewall (10.7 and later) or Start (10.6) to enable the firewall. Click Turn Off Firewall (10.7 and later) or Stop (10.6) to disable the firewall.

Mac OS X 10.5

Step 1:

Image result for mac os x firewall

From the Apple menu, select System Preferences…. When the System Preferences window appears, from the View menu, select Security

Step 2:

Click the Firewall tab.

Step 3:

If the orange padlock icon in the lower left side of the window is closed, click it, and then authenticate with your Mac’s administrator username and password. This will allow you to make changes.

Advanced settings

Image result for mac os x firewall

Block all incoming connections

Selecting the option to “Block all incoming connections” prevents all sharing services, such as File Sharing and Screen Sharing from receiving incoming connections. The system services that are still allowed to receive incoming connections are:

  • configd, which implements DHCP and other network configuration services
  • mDNSResponder, which implements Bonjour
  • racoon, which implements IPSec

To use sharing services, make sure “Block all incoming connections” is deselected.

Allowing specific applications

To allow a specific app to receive incoming connections, add it using Firewall Options:

  1. Open System Preferences.
  2. Click the Security or Security & Privacy icon.
  3. Select the Firewall tab.
  4. Click the lock icon in the preference pane, then enter an administrator name and password.
  5. Select the Firewall Options button
  6. Click the Add Application ( ) button.
  7. Select the app you want to allow incoming connection privileges for.
  8. Click Add.
  9. Click OK.

You can also remove any apps listed here that you no longer want to allow by clicking the Remove App (-) button.

 

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