[Myth] Captchas for detecting robots!! Are they efficient?

Last update on August 16, 2009 01:35 AM by fahd_zboot
Published by deri58

Captchas for detecting robots!! Are they efficient?





Captchas are images containing letters to be submitted for proving that the user is a human. They are usually installed to block bots (automated software).

Myth


Captchas can block 100% of the robots.

Reality


FALSE

Explanations


Captchas are moreover effective but not at 100%. Below are lists of reasons for proving same:
  • They are sometimes poorly implemented (sometimes found the answer in the URL of the image, or the captcha text ...!)
  • Character recognition has made enormous progress.


Captcha bad, easy to decode:



Good captcha difficult to decode:



Captchas are not absolute protection against robots. It is necessary to plan carefully its captchas, or adopt additional protections.

Spammers have nowadays managed for solving 20% of automatic captcha for Gmail which is one of the best.

In addition, captchas create problems:
  • Some captchas are sometimes poorly planned and even unreadable by humans which is frustrating for users visiting specific site.
  • A side effect is that it makes the site inaccessible to blind people because they use software synthetic speech or Braille however based on the text which however alternatives.
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