All that spam on the Internet these days gets sent by ?owned? boxes, usually Windows-based home computers. Cyber pirates scan for easy-to-compromise machines. Tiger?s built-in personal firewall protects your computer from unauthorized access by monitoring all incoming network traffic. When you enable the personal firewall in Mac OS X, all inbound connections are denied except for those that you explicitly permit. And now with stealth mode, your Mac won?t even acknowledge its existence to people scanning for machines to attack.