Security advice needed
 

Hi,

I've got a question about security. What possibilities are there to check a new member?

On my forum, everyone can join, but I want to know if there are ways to check the information given by that new member.
Are there ways to see if an IP-address or an email address are realible?

Are there any other ways I should think of in order to protect the forum against weirdo's and other dubious members?

All help and ideas are very much appreciated since I'm new into this!