Corsaire, an organization devoted to securing information systems, has published a white paper on how to harden Mac OS X Leopard. The guide includes security guidelines, monitoring with Common Criteria Tools, managing users, system security settings and more.
According to the document, the author, Daniel Cuthbert, "heads up Corsaireis Security Training and has over nine years of industry experience. During this time he has focused on Security Assessment for some of the worldis largest consultancies and financial, telecommunication and media institutions."
From Corsaire: Securing Mac OS X Leopard (10.5)
The 57 page document can be downloaded as a PDF file. It includes references for hardening Leopard, open firmware, Appleis firewall, the file system, and network services.
The paper is, unfortunately, weak on using the Common Criterial Tools, and more complete tutorials can be found elsewhere. On the other hand, the paper is much stronger at showing how to use the security features of Mac OS X to harden the system. A good knowledge of the UNIX command line will be required.
Mac IT administrators are likely to be aware of these techniques, but itis always a good idea to have multiple sources of information and references. Not every paper like this covers every topic, and tidbits can always be picked up.