How do you prevent linking to attachment.php?

[ImportPassion.com]

I would like to do one of 2 things.

Stop ppl being able to link their attachment offsite or let them do it, but add watermarks.
The latter being more preferable.

Thanks,
D

[conqsoft]

There's a plugin on vbulletin.org to add a watermark.

To prevent linking, just deny access to attachments for your Unregistered usergroup.

[ImportPassion.com]

I only want to add watermark if it is being linked remotely tho. not every image on the site.

If I do that, guests won't see attachments on the site.

[Freesteyelz]

How about Hot Link protection using .htaccess?

[ImportPassion.com]

I tried adding php as an extension along with gif etc., but it screwed up. can't remember what exactly tho.