Breaking down a Captcha
Traditional captcha systems have several weak points that take away from
their potential effectiveness.
- Images are difficult for humans to read
- Images are readable to some bots (programs made to spam your site)
- Reliancy on 3rd party APIs such as flickr
- Exclude users who choose to disable javascript
I have heard many complaints from site users and communities about
the ineffectiveness of today's captcha systems. In theory, using flat
pictures (not text) to separate the humans from the robots is an
excellent idea. The problem, however, is that spam is profitable and anywhere
there is money ... crackers are close behind ready to exploit the system. These
guys are smart enough to write programs that recognize text inside a picture
which renders traditional captcha programs useless.
Why is AnimatedCaptcha any better?
Because this captcha is not a single image, it keeps the robots guessing.
Traditionally, for a program to break into a captcha, it would have to
read the picture pixel by pixel and look for combinations of pixels of the
same color. From here, bad bots can stitch those colors together and
recognize letters as patterns of colors.
By making the above images a series of pictures (called an animated gif),
it makes breaking into this captcha system very difficult. Why is it so difficult?
- The number of frames created are totally random
- The elapsed time of the animation's rotation is random
- The numbers (1-9) and operators (plus [+], minus [-] & times [x]) are also chosen at random
There are 125+ different combinations of questions by default.
This system is also superior to traditional captcha images because it is very readable to
humans and complete an total jargon to programs. Usually the text in a captcha is contorted or placed on a very busy background,
this leads to an unreadable capcha (expecially to the visually impared). AminatedCaptcha fights
bots by using multiple layers instead of 1 flat picture. Confusing to bots but shows up as plain letters
on a white background which makes very easy on the eyes.
As an additional benefit, the frames are numbers instead of letters which allows for
- Captcha to be multi-linugal.
- Questions easy enough for any 3rd grader (~10 years old) to answer.
- Never again confuse the characters 1,l,I,0,O and many other tricky alpha-numeric options.
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