If you care about your campaign, maybe you should limit the criteria of Newbie accounts that apply. Even newly created accounts you accept, it's like you intentionally attract cheaters to participate in making your campaign successful.
This would not stop cheaters doing the same cheating like usual, they only need to upgrade to jr.member rank or get those accounts in some other way.If they are willing to do this cheating for extra $5 than they can do much worse
I would not accept any inactive members, and I would take a look at forum history of all participants.