Required software development freelancer for System administrator, Wordpress malware removal job

I have a shared host, which hosts several domain names. All of them have a Wordpress website.
They occasionally get attacked and infected by malicious unknown attackers. As a result, core files such as functions.php file in all themes get infected. It is really annoying, because our host company will suspend the whole account.

I need someone who can prevent it from happening and teach me how to do it.
I also need to learn how to clean the infected files.
It is an ongoing project for the right candidate, because I urgently need a Wordpress security expert who can help me maintain my various websites.
Thanks

Skills & Expertise Required

software development