Secure Administrator is a great plugin to hide your Joomla Sites Backedn from unwanted visitors.
It is very simple and easy to use but powerful plugin
Plugin is Very Easy to use!
All you need to do is :
*** Installing the Plugin via Joomla Installer
*** After Installation, Set Parameters via Plugin Back-end
*** You can set / control all via back-end
*** Set up a secret word for your backend url
*** Enable - Disable to login via only selected IP Address
*** Prevent - Block IP Adresses
*** Log to a txt file who tried to login to your backend
*** After completing settings Publish the module
*** For style customizations; there is a css file
*** You can ask for support at community forum when you need help