1) Open the Apple Menu.
2) Click System Preferences...
3) Click Security.
4) Click the Firewall tab.
5) Unlock the pane by clicking the Lock icon in the lower-left corner and enter the administrator username and password.
6) Click Start to enable the firewall.
7) Click Advanced to customize the firewall configuration.
8) Click the + button to add additional applications.
9) Find the application you want to add, then select Add.
10) Make sure that Automatically allow signed software to receive incoming connections is checked.
11) Repeat the same steps for all Blizzard applications, then click OK.
12) Click the Lock icon to save changes.
You can now close all the windows you opened. Congratulations! Your firewall should now allow traffic for proper World of Warcraft and Blizzard Downloader operation.
