If you plan on having more than one computer, get a Linksys or Netgear (or other brand) router and use the router as the firewall. If you get a router, you don't need to use MacOS X's built-in router.<br><br>If you only have one computer, use the MacOS X firewall. By default there isn't much open on MacOS X to worry about. Turn off all sharing you don't need (which is off by default) and you should be fine.<br><br>