We’ve seen numerous WordPress installations that have been hacked where the hackers have uploaded secret files into the wp-content and wp-includes folders that are named similarly to actual WordPress filenames, but are actually shell, malware or even mailer scripts which allow the hackers the use of your hosting account for their own devices. These PHP scripts can wreak havoc on the server environment, get your IP blacklisted and force server admins to take your site down. Here’s one tip we recommend to help prevent this from happening.
In order to block hackers from executing PHP scripts in these directories you can create an .htaccess file in these directories which tells the server PHP should NOT be run in them directly. Here’s the code to place in a blank .htaccess file:
<Files *.php> deny from all </Files>
You can then upload that .htaccess file to your wp-content and wp-includes folders.
Please Note: uploading this file to the wp-content folder can cause an issue with some themes and plugins, especially those using timthumb.php directly. If that’s the case, just delete the file and all will be fixed.