[Awjvail]

in .htaccess put the following:

RewriteEngine on
# Options +FollowSymlinks
RewriteCond %{HTTP_REFERER} badsite\.com [NC]
RewriteRule .* - [F]

replace badsite with the site you want to block.

multiple domains:

RewriteEngine on
# Options +FollowSymlinks
RewriteCond %{HTTP_REFERER} badsite\.com [NC,OR]
RewriteCond %{HTTP_REFERER} anotherbadsite\.com
RewriteRule .* - [F]

Note the backslash before the domain.

If you don't have a .htaccess, you should create one and place it in your vB directory.