For a while now, we’ve been encouraging users to use .htaccess to protect their Joomla administrator folder to help protect a number of attacks. This only takes a few minutes to setup an can save you hours of hassles down the road. In order to protect the server and other customers sites if we notice hacking attempts on unprotected administrator folders, we will chmod 000 the entire administrator folder without notice. This change will not affect your main site in any way, it just affects the administrator. If you notice a 403 Forbidden error when accessing your administrator, it means we have changed the permissions.
To protect your site, all you need to do is enable password protection on your administrator folder. This tutorial walks you through setting it up: How do I password protect directories?
If we have to block access to the folder, you can enable it again when you need by just changing the permissions. After you change the permissions, make sure you protect the folder to prevent future interruptions. To change the permissions, use the cPanel file manager, select the administrator folder, click Change Permissions, and change them to 755. If you’re unsure how to use the file manager, we have a tutorial here: How do I use the file manager?