Pictures Attached to posts are displayed in [IMG]?

Sorry for the noob question but what mod is that? I've seen posts on here where the picture attached is displayed within [IMG] tags in the post. I've searched on here and on vborg with no joy.

That is default vBulletin. You wrap the image URL inside of the img bbcode.

Silly me never realised you could do that with attachments as well, thanks Michael.

This is the first site that I've come across that does this, so I'm curious as to why? since the user can click on the attachment and view. Just for convenience and for guests viewing?

Since it's already attached there is no cost I take it but the worry about hot-linking? Which I can stop by .htaccess I believe.

Many sites have it this way, it all depends on how the user chooses to add the image.