even discusses why you might not want to use them[http://tldp.org/HOWTO/Security-HOWTO/—A must-read HOWTO](http://tldp.org/HOWTO/Security-HOWTO/—A must-read HOWTO)
that provides a good overview of security issues, including creating
accounts, file permissions, and password security
[http://tldp.org/LDP/sag/html/index.html—A general guide, the Linux](http://tldp.org/LDP/sag/html/index.html—A general guide, the Linux)
System Administrator’s Security Guide has interesting sections on
limiting and monitoring users.
[http://www.kernel.org/pub/linux/libs/pam—The Pluggable Authentication](http://www.kernel.org/pub/linux/libs/pam—The Pluggable Authentication)
Modules suite contains complex and highly useful applications that
provide additional security and logging for passwords. PAM is installed
by default in Ubuntu. It isn’t necessary to understand the intricacies of
PAM to use it effectively.