This is what I was looking for.
Now that I had been using it for a while, I must say it works PREFECT. It was the solution for my comments spam problems. Tried Captchas and Mathematical protections, and I must say this is a great solution, much cleaner for the commenter and way more effective for me.
But I still point this...
One thing I would like is to have multiple questions and not just one. Having that, then I will make my review to 5 stars ;)
Thanks to the authors for this simple and effective plugin.