Learn about it:
The DoorStop X Firewall
The Mac's first firewall
Protects your Mac from outside attack
Easy-to-use interface means less chance of mistakes
Critical improvements to OS X's "built-in" firewall
Available standalone or as part of our integrated Security Suite
DoorStop X is designed to work with our Who's There? Firewall Advisor and book "Internet Security for Your Macintosh" as part of the DoorStop X Security Suite.
Open Door Networks has been securing the Mac since 1998 and Mac OS 8. We literally wrote the book on Internet security.