Protect user edit form (profile fields)

Hi,
I'm seeing several new users registered into my site. I had the Captcha module, which seems to be not too hard to guess (I was using the 5 + 2 =...).
I installed Mollom, and now they are answering the image verification. They can overtake this, creating an account. Here, no one can know if it's a bot or not. But then, all users go to edit their profile, and put links to spam websites (rolex, pills, ...) in a text field in the profile.

Can mollom show a captcha there to prevent that? The problem is that maybe they can also answer that captcha... I think I need something to analize the URLs...

Any help will be appreciated!

Thanks