Question: I run a large bulletin board and I get spammers every now and again. My moderation team does a good job filtering them out but every time I IP ban them they seem to come back (I'm pretty sure it's the same person on some occasions, as the post patterns are exactly the same as are the usernames) but I'm afraid to ban them by IP address every time.

If they are on a dynamic IP address, I could be banning innocent users later down the line when they try to get to my forum through SERPs, but if I ban only via static IPs I know that I'm only banning that one person.

So, is there a way to properly determine if an IP address is static or dynamic?

Thanks.

Answer: 
No, you can't tell if an IP address is static or dynamic. Any time you IP ban a user, you run the risk of banning legitimate users.

If the IP addresses are from out of country, especially from a region that you aren't targeting demographically, I say block away.

If you can prevent automation, that will help a lot in fighting spam, at least enough for your moderators to keep up.

Make sure that you are using the [nofollow](http://en.wikipedia.org/wiki/Nofollow) link attribute when displaying user posted links. This will prevent the spammers from improving their SEO scores in the time it takes to delete the messages.

Many BBs allow you to specify that the user can't post any links until they've posted a minimum number of messages.
You can try to do DNS resolve the ip address and see if it match some terms which identify the IP as a dynamic (adsl, cable, dialup, dyn) or static (static, server, biz).