First of all, let me start by saying that you should probably NOT do this. There are many files from the core and other 3rd party extensions that make reference to the /administrator directory. Renaming this directory means having to find all of those references and changing them to the new name, and also changing the reference in any new extension before installing. I’m basically writing this because I know there are many of you out there searching the web on how to do this, and eventually a few of you might stumble upon this article. So it’s almost like a bait-and-switch, but not a 100%. I will still give some recommendations if you’re paranoid about everyone knowing that your Joomla site has an accessible /administrator directory.

Apache’s .htaccess to restrict access
You can setup and .htaccess inside of your /administrator directory to add a second layer of security. This file can be setup to allow access based on username/password or even IP address. The IP address part is good if you or other users are going to access the /administrator directory from a fixed IP at all times. Of course I’m not going to go into specifics on how to setup a .htaccess here, but you can start by clicking on the following link: .htaccess password generators