title: How can I prevent SPAM users from signing up?
body: <p>I have a website that is starting to grow but with that comes users who continue to signup and send SPAM messages to other members. I currently use google's captcha API service but if a user creates an account manually then it's of no use.  My main problem is after a user creates a fake account they start sending duplicate messages so my thought here is to check with some PHP code for similarities in messages and deny them after x amount sent but I'm not sure how much of a load this puts on the server.  Is there a way I can maybe grab the IP when they signup and ban that IP if they start spamming people.  It's driving me nuts because I spend almost an hour a day now cleaning up SPAM and removing invalid users.  Have others run into this and what measures have you taken?</p>