Sir, the purpose of the software is only to defeat the intention suggested by you. If you go through the wikipedia link, you fill find that earlier captcha images of Yahoo could be copied and entries made. Therefore Yahoo introduced a line across the letters. The captcha software requires the letters to be entered from the key board and not the distorted characters copied. But the police and thief game is always on in the software industry. There may be some nerd who is working on or already invented a method to circumvent the captcha requirements.