Lockdown WP Admin conceals the administration and login screen from intruders. It can hide WordPress Admin (/wp-admin/) and and login (/wp-login.php)
If your WordPress installation is in a subfolder, the plugin doesn't quite work as advertised. The changed login URL is correct, but once you enter your credentials on that form, you get a 404 page. However, you are actually logged in at this point so you can manually type an admin page to head to, which is a serious annoyance.
This is yet another plugin that can't properly use site_url() and home_url().