Security Assist
You have to protect the admin directory. The easiest way to do that would be to use Security Assist. This would require users to login before they could see anything in that folder.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.