There are a couple of things that we could do in regards to this. First, I looked in the back end and I noticed that the feature that scans the IPs of new users against the banned IP list has been disabled. This is something that we can turn on if you guys like so that way it will hopefully catch a few others that are registering with a potentially bad IP address. This is particularly useful when using the OTB feature.
Second option is that we can add the cyb- Advanced Permissions Based on Post Count plugin where we can set it to block links from being posted until users reach x# of posts.