How can I restrict access to certain threads unless member has made several posts?

I would like to restrict access to new members and members who don't participate on forum activities but just take what they want and never post a message/topic or game for other members. I would like to do this by restricting them access to the important threads only until they have made the required number of posts. Should they click on the restricted threads, I would also like a pop up window saying that they do not have access rights until they have fulfilled the requirements or something like that.

Can this be done?

I'm sorry but you can only restrict forums and not threads.

Thank you for this. Will put up as a suggestion then.

Is this solved?

Yes.