drugCMS

Create a folder named "system" in which the system files and folders get moved.
Only the client folder(s) remain in root.
The new folder must be renamed on setup, so only the sysadmin knows it's name.
In this folder, there must be a .htaccess which routes to the /<new folder>/drugcms/ folder.
The drugCMS backend then is reachable only by entering this folder's name after the domain.
CAUTION: The client's config.php file needs to be altered as well!

As the setup folder get's moved into this new folder too, setup has to change it's address on the renaming process in order to continue.

On (cross-)upgrading from drugCMS 2.0.x/Contenido 4.6.x and 4.8.x, we have to remove the old system folders and files, as they are not within this new folder.
And in this situation the sysadmin (who does the upgrade) also has to enter a new name for this folder, except if he removed it and moved the contained system files and folders back to root (he might already work with a subdomain for the backend).