Banning Users AND keeping their posts/threads hidden?!

[Crazy Serb]

Is there a hack out there already that allows me to ban (or delete) users and turning all their posts/threads to hidden (only visible to mods/admins/certain usergroups) status as well? Or moving them to this 'ignored' usergroup where they keep on posting on the board unaware that all their posts/threads are hidden from others?

I know that if you delete a user all his posts remain public under the nickname "Guest", but I want to be able to keep them on the board but invisible to most visitors (just for further reference, in case I need to actually refer to something they posted later on).

I thought I saw something like this around here, but am having trouble finding it now...