Found this - Moderate New Registrations Based On IP Geographical Origin - vBulletin.org Forum that might work with this version of vB (4.1.7). If the rash of spammers are coming from a handful of countries (Russia, China, etc.), this would help out. Can set it to require moderator approval of new users from specific IP ranges, while other users (i.e. those in the US/Canada) will not require moderator approval. Considering the vast majority of users should be located in the US, it should help reduce the amount of spam.