Malware files appear in files

How do I make wordpress work well without being able to create a new files or edit a files in the entire wordpress directory? I want to avoid viruses because recently I get malware files, I deleted them, a few days later there are appear again, or a malware code lines is written to wp-settings.php, now wp-settings.php i changed chmod to wp-settings.php to nobody can write in file.
I used most populars malware clean plugins to clean wp even reinstalled whole wordpress but same result, i also have multiple wordpress on that hosting.