Hello, @thinknew

I will recommend you to check the folder’s structure and make sure that the permissions are not set too high. This should prevent people from accessing certain directories and also prevent them from uploading files.

Another thing is to disable shell_exec . The shellexec() function is an inbuilt function in PHP which is used to execute the commands via shell and return the complete output as a string. When it’s usually enabled people can use it to execute malicious scripts. In order to disable it open the PHP.ini file and add the shellexec to the disable_functions row/line:

disable_functions=shell_exec

You’ve mentioned that the sites are based on WordPress so there are several things you need to do:

1. Always make sure that your WordPress installations are up to date. When there is a new update you can take a backup (in case something goes wrong) for the site and then update the WordPress version.

2. Keep you plugins updated. When there is a new version of a plugin that you use, update it. You can again first take backup for the site in question.

3. Remove any plugin which is not active. If you have any plugins which are currently inactive and you’re not using it will be better to have this removed.

4. Install a security plugin like Wordfence, iThemes Security or Sucuri Security to keep everything protected.

5. Occasionally checking through the site files for the sites, making sure nothing is out of place

You can also check the status of your sites site checking them through hack scanners such as http://sitecheck.sucuri.net/ http://isithacked.com/ http://www.unmaskparasites.com/

Hope this helps!

Regards,
Alex