Earlier this summer, Apple published its Apple's Mac OS X Security Configuration for Version 10.5 Leopard guide. And anyone who is interested in keeping their standalone 10.5 installation secure should take a look. The 240-page PDF is a security tome aimed at the more technically inclined. That guide is available here if you're interested.
While the Mac OS X Security Configuration for Version 10.5 Leopard guide is good for securing standalone systems, a security guide published today by security firm Corsaire helps to better secure networked OS X 10.5 installs. But just like Apple's own security guide, this one also requires some technical acumen:
The reader should be familiar with using the Unix command line and editing plain text configuration files. Most of the operations require administrator access and Corsaire would recommend that each file be backed up before it is edited.
For anyone interested in OS X security, and especially admins tasked with securing networked Macs, this one is worth a read. It not only provides a solid overview of the new security features in OS X 10.5, but also is a good primer on hardening the OS, managing users, and how to log and audit security-related incidents.