DDT on "[Plugin: Contact Form 7] Any are-you-human question add on??"

Hello,

I am getting spam from the contact form 7 on my website. I have installed recaptcha (from google) but still it doesn't prevent the spam.
So now i like to try the are-you-human kind of questions, for example "what number is between 7 and 9"

Any cf7 addon available?

regards

http://wordpress.org/extend/plugins/contact-form-7/