Have they tried using some kind of cPanel? That usually helps out in this kind of situation. I advise my clients to get a
cheap cpanel license. You should do the same. If you don't know what that means, well, it's a suite of tools built for Linux OS that gives you the ability to automate web hosting tasks via a simple graphical user interface. They can avoid all the complexity of creating advanced server configurations because it comes equipped with automatic updates. Also, the one I linked here prevents malicious software from trying to muscle through your password security with cPHulk.
