Spammer signups... new possible way to identify / ban?

[kryptonbulbs]

I have noticed that every or at least close to every spammer I have banned or globally ignored on my website has put their username in an additional field I have set up. My website caters to Yamaha Motorsports and a profile field I set up is "toys" so users can say what kind of bikes, or 4 wheelers and whatnot they have.

Most every spammer that has signed up has put their username (identically) into this feild.

I was wondering if there is any way to write some code to either automatically globally ignore, ban, or at the very least notify me (admin) that a user has entered this field to be the same as their username.

Any help is appreciated!