Hi am posting this thread to ask if any one has an idea of how to harden the security of a Samba server which servers as a login Auth server and also as a file server in a windows network.
any contributions would be highly appreciated

Most distro's will package Samba 3 books either with samba or in a separate samba-doc package. Chapter 18 in the "The Official Samba-3 HOWTO and Reference Guide" deals with securing samba. Also be sure to lock down the server itself, removing unnecessary services, keeping software up to date, etc. There are books on securing Linux that you probably want to read.

In my opinion, the area that needs the most improvement is in programs that could be susceptible to user input overruns, such as sql injection. Not running a web server or database on the same server would help secure it. If another service is compromised, the samba service could be compromised as a result.