I'd suggest implementing a CAPTCHA instead. In English, a
verification code image which displays a few distorted letters and
numbers on a messy background, which (hopefully) only humans can
interprete, not automatic OCR engines.
Since CFMX 8 (codename Scorpio) will introduce built-in
support for CAPTCHA images, and my own secret world-dominating
CFMX-based content management system is anything from ready, I
haven't had to worry about the issue yet, but do a web search for
"Coldfusion captcha", and you'll almost certainly find a solution,
I'm sure.
If it's only the module that's attacked, and not an actual
web page, then you need to tighten the security of the module which
is handling the posted form.
Hope this helps, and fits your framework.