Me and another Admin of my forum are wanting to open the community up a bit more by allowing guests to post, however there are several trouble makers that would try to take advantage of the "anonymous" aspect. We would like to disallow them being about to post as guests. We know their IPs and are just wondering if there is a hack or if someone could make one to block those ips or ip ranges from being about to post as guests or even be guests in the first place.
You will be able to tell whose those trouble makers are when they post. Do an ip check on the guest to confirm, then send a warning to them at their main user account.