Add a box in a custom plug in for Wordpress to prevent spam

We are looking to get our custom plug in that we had created to add a box where they user is required to type in text from an image before they can submit the form submit. we would like to insure that we can insure the random words or text are not predictable and change the list of words or text images. Also we need the option of how many time they can submit before we tell them that it is not submitted... We need to have the custom plug in updated and repackaged so we can reinstall in new Wordpress 3.4.1 systems. This must include the details on how to install and where the file locations are. Current form [login to view URL]