Ever failed reading these nasty distorted numbers and symbols while creating a new account or entering a comment on your favourite blog? Captchas are a quite efficient way to separate spamming bots from real users because the last one usually would be able to read the letters while the first one should be not. Unfortunately, times changed. An increasing number of bots acquired the ability to examine even twisted letters in a captcha image and continued spamming. As a consequence of this, captchas got more and more unreadable, even to the common human reader, thus rendering captcha protection impossible. New captchas will present pictures instead of text, and in the near future you'll be presented pictures with cats and dogs where you have to choose the right images. This kind of task is extremely difficult for software (i.e. bots) and so the next turn in this neverending fight between them and us is being heralded. Hope they provide a Perl module soon! (Source)