To block image leachers, I do:

<VirtualHost ...>
...

<Directory /var/www/html/site/images>
RewriteEngine On

RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^.*mydomain.com.*$ [NC]
RewriteRule .*$ /leacher.gif
</Directory>

...
</VirtualHost>

Is there a way to set it up so it applies to all virtualhosts? Put it in a <Location> container?

PS, any tips for more effective leach blocking are welcome .