After analyzing all available captchas at the moment our team came to the conclusion that you have the right not to spoil your eyes staring at pictures and created a unique simple CAPTCHA with means of math logic, easily understood by human beings.
The Captcha plugin allows you to implement a super security captcha form into web forms. It protects your website from spam by means of math logic. You will not have to spend your precious time on annoying attempts to understand hard-to-read words, combinations of letters or pictures that make your eyes pop up. All you need is to do one of the three basic maths actions - add, subtract and multiply.
This captcha can be used for login, registration, password recovery, comments forms. There is also a premium version of the plugin, allowing compatibility with BuddyPress (Registration form, Comments form, "Create a Group" form).