I've been getting spammed by a Robot alot here lately... When a member signs up there required to fill in all of the blanks(username, name, email, etc.). I want to make it where certain characters cant be used in this area(such as < / " etc.) I also want to require an @ in the email space. The robot is filling in random info and a link to some product. I'm getting tired of it, I've tried blocking the IP, but the same spam comes from many different IP's.

Add a captcha
http://recaptcha.net/

such check needs knowledge in regular expression. what I know is that you can validate any pattern you set in your Regexp. So check it out for I'm not well versed in it.

May be look at these:
http://lmgtfy.com/?q=regular+expressions