[Marco van Herwaarden]

vBulletin already comes with some sort of standard "Hot Linking" protection.

Consider the following:
- you can already deny downloading of attachments to guests. Hotlinking to attachment.php will have no real use, as it would still require a member login to download.
- If you are storing attachments in the database, then the above would be enough.
- If you are storing in the filesystem, your attachment directory should be located above the webroot. This would make direct linking to the attachment impossible.
- Even if stored in filesystem and under webroot, then using a .htaccess rule to prevent acces to attachments from outside links would be the best way to do it.