WordPress | Block Spam Bots With No Referrer | htaccess

# Protect from spam bots
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{REQUEST_METHOD} POST
RewriteCond %{REQUEST_URI} .wp-comments-post\.php*
RewriteCond %{HTTP_REFERER} !.yourwebsite.com.* [OR]
RewriteCond %{HTTP_USER_AGENT} ^$
RewriteRule (.*) ^http://%{REMOTE_ADDR}/$ [R=301,L]
</IfModule>

# http://www.mastermindblogger.com/2011/5-simple-tricks-to-prevent-wordpress-spam-comments/
# Saved here to keep it accessible to myself.