If you use Macintosh OS X, CUIT recommends that you use the built-in OS X firewall to help protect your computer from viruses and worms.

1. Open System Preferences by selecting it from the Apple menu or clicking it in your Dock.
   
   
2. Select Sharing from the Internet & Network preferences section.
   
   
3. Click the Firewall tab and click Start. It will say Firewall On above the button once you've activated the firewall.
   
   
4. You may allow access to your Mac on a service-by-service basis by selecting the individual services in the Allow box. If you don't understand what any of this means, you should make sure that NONE of the services are allowed.
   
   
5. Quit System Preferences.

Apple Article on Mac OS X Firewall

To reach this page quickly in the future, use the keyword macfirewall.

Send reports of security incidents, attacks, or questions to security@columbia.edu