Per ITS policy, all Macs on SU's network should have a firewall enabled.  You can enable it using the following instructions:

Locating Security & Privacy

1. From the Apple Menu, select system preferences (or use the system preferences icon on the dock).
2. Select  "Security & Privacy."Go to the  menu in the top left corner of your screen > System Preferences
   
   
3. In System Preferences, select Security & Privacy
   
   Image Added
4. Select the "Firewall" tab.Click the
   
   Image Added

5. If you Firewall is off, click the button that says "Turn On Firewall On" button.

   Note
   title Unable to turn on your firewall?
   Make sure the screen says it is unlocked for changes.  If not, click on the lock icon in the bottom left corner of the window to unlock the settings (you may . You will be prompted for to enter the administrator password )for the computer.

6. You will now see a screen indicating that the firewall is turned on.If the Firewall has been turned on, you will see a green light and the wording Firewall: On
   
   
7. Click on the lock icon to lock down the settings.