I don't know if this is already a feature but it would be nice if some forums (e.g. spam forum) can be excluded from any search (new posts, etc) on the forum.
It's already possible. For those forums you want excluded, edit the forum permissions and for each usergroup deselect the permission "Can Search Forum"
@Dennis
Is that globally or per user?
members under the usergroup which u select it.
vinoth is correct. If you deselect "Can Search Forum" from the Registered Usergroup on Forum X for example, then users in that usergroup will not be able to search that forum, but they will be able to search other forums.