Contact Form Spam

Hello to everybody.

I have a problem with spam in contact form.
The model, Controller and view is the basic one from installation, nothing is change.
captcha is there and work.

How are they passing captcha? is not possible they are doing manually because is just a contact form and everyone can see it, is not a forum or something like that.

Some suggestion about this problem?
Thank you

Are you sure your captcha is required in your rules?

You could add a honey pot: a hidden field that is supposed to stay empty. Most bots would fill it with a value, so you could use that fact: if there’s a value in this field, then it’s spam.

Or you could try another Captcha extension like:

I wonder how they doing it could be something with your rules or maybe they are doing something crazy like image recognition, you could try recaptcha as suggested by @machour