#BLOCKING BELOW DOMAIN NAME FROM SENDING TRAFFIC TO OUR DOMAIN NAME
RewriteEngine on
RewriteCond %{HTTP_REFERER} externaldomain\.com [NC,OR]
RewriteCond %{HTTP_REFERER} www\.externaldomain\.com
RewriteRule .* - [F]
[NC] tells server not to take domain name as case-sensitive. OR lets you add another domain name within same code, we have added www instead.