Here's a white paper on making Apple's Mac OS X 10.4 more secure.
Mac OS X 10.4 Tiger provides one of the most secure default installations of any desktop operating
system. The operating system also includes numerous features and additional tools to help users
manage the security of their data. The install follows the accepted best practice of disabling all
network services unless explicitly enabled and the default security settings should suit the needs of
most users in a workstation setting.