However challenging it is to keep up with all facets of computing security, a few areas have matured enough to be worth learning methodically. The first one I recommend to anyone working with Linux servers is account management.
Many of the first wave of books devoted to Linux administration and programming included a chapter on "user management" or "account management." Their meaning was rather specific: how to set up and maintain the computing accounts and group affiliations for the people who use your host.
The link for this article located at IBM is no longer available.