The National Security Agency (NSA) has published version 2 of its security guidelines for Mac OS X. The security documents are available in PDF format on their OS Guides page for Mac OS X.
These documents for Mac OS X and Mac OS X Server represent best practices for securing the OS and are widely used by the industry as internal standards for configuring Mac OS X. The document is actually written by experts at Apple and endorsed by the NSA which says on its Website," It is our belief that these guides establish the latest best practices for securing the products and recommend that traditional customers of our security recommendations use the Apple guides when securing Macintosh OS X 10.4.x and Macintosh OS X Server 10.4.x."
Practices such as setting up admin accounts, generating passwords, the proper way to remove Classic, which can be a serious security problem for Mac OS X, managing the root account, and the use of Access Control Lists (ACLs) is covered.
Out of the box, Mac OS X is fairly secure, especially with respect to closed ports. However, for those in the enterprise who want to take advantage of every feature of Mac OS X to lock down and secure the OS against not only network but local intrusions, this is a must read.