Whitepaper on hardening Mac OS X. The paper includes a very brief introduction to the firmware, descriptions of hardening using both GUI and command-line interface.
You can download it from the following link: https://packetstormsecurity.com/files/download/33767/040622-securing-mac-os-x.pdf
Source: https://packetstormsecurity.com/files/33767/040622-securing-mac-os-x.pdf.html