Disable comments after xx days

I receive waaayyy too much spam – often picked up by crawlers, and therefore in old posts.

I’ve seen a plugin that can disable comments when a post have been active for a certain amount of days, but can’t seem to find it.
Anyone?

(or another, better spam-filter that means that I don’t have to manually delete 400 comments every morning 🙁 )

It’s for WP1.5.x.

Thanks,
Anders