I use this as anti-hotlink protection for images:

Code:
RewriteEngine on
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http://example.com/.*$ [NC]
RewriteCond %{HTTP_REFERER} !^http://example.com$ [NC]
RewriteCond %{HTTP_REFERER} !^http://www.example.com/.*$ [NC]
RewriteCond %{HTTP_REFERER} !^http://www.example.com$ [NC]
RewriteRule .*\.(.*.*.*gif|jpg|jpeg|png|bmp|tif|tiff)$ http://example.com/403.shtml [R,NC]
This example blocks entire file extensions. As an alternative, does anyone know how to change the info in the last line of this so that it will block access to a specific file such as example.jpg or even example.php?