Spider Bots are useful, though. They are the ones who make sure new information, new threads, etc go up on their respective search engines. For example a Yahoo Spider will continually update the search results on Yahoo! so let's say someone types in "metal junk fetish" in the Yahoo search engine, they will more than likely get a result to link back here to the metal junk thread that was just recently started. If you take the spiders off there will be no redirection to new posts that contain information which people might search out. I haven't noticed too mcuh spam happening here, even on my forums I think I had more bots and it is way smaller than this place. Something that I did was to set it up that people are required to post at least 2 times into topics before ever being able to start their own new topic. Spam bots don't want to, and generally aren't set up to, post more than once and when they do it is usually just to start a thread. And also turned off automatic email notification for private messaging. This keeps users from receiving the email copy of the private message containing the spam.
I think the way you have it set up right now, not accepting any new members, is the most secure means of making sure Spam bots do not come our way but as a forum Admin I am sure you would still like new users to keep this forum more active and growing so "no new users" is always bit of a nuisance in that respect.
