I am not at all an expert but you may start securing php and I removed comment form on my site.
I started by setting .htaccess to specific IP ranges. if I have to edit because I am away I can always cpanel and edit the file remotely.
code I used in my .htaccess
# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ – [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
also added <Files wp-login.php>
Order Deny,Allow
Deny from All
Allow from ##.##.##
Allow from ##.##.##
Allow from ##.##.##
Allow from ##.##.##
Deny from ##.##.##
used same IP list for
<Files wp-admin$>
Order Deny,Allow
Deny from All
again same IP list
</Files>
<FilesMatch “^php5?\.(ini|cgi)$”>
Order Deny,Allow
Deny from All
(ended above with)
Allow from env=REDIRECT_STATUS=200
last was
</FilesMatch>
Options -Indexes
<Files xmlrpc.php>
Order Deny,Allow
Deny from all
</Files>
with my new host the first section broke the site due to updates, it worked with my old host.
wordfence has helped a lot but it’s not the cure all.
if you have not added this to your .htaccess or restricted it.. it will most likely continue. I believe the code was tossed at the contact form and pulled via PHP commands.
if you have done this.. thats about it for me. if not do so and clean the site again.