If you want to have a completely locked down area of your webapplication which can only be accessed by administrators from your company, then SSL authorization maybe for you. It will insure that no one can make a connection to the server instance unless they have an authorized certificate installed in their browser. Last week I wrote an article on how to setup the server: Article
This is one of the most secure setups you will find as there are no username/passwords involved so no one can gain access unless one of your users hands the key files to a potential hacker.