Please copy the word in the box before continuing

[slimfandango]

2 questions.
Why can't software be written that defeats this security measure. Seems like a cinch.
What is it that lets the human brain read it where software fails?
What is the point of the weird colours? And the cross hatching?
Actually that's 4 questions.

[Mattk]

because to another computer it isnt text its a random pattern but to us it makes sense as the pattern takes the appearance of numbers or letters

[slimfandango]

A �48 scanner from Dixons has Optical Character Recognition that pulls out text from a 'picture'. I know what the function does, I don't know how it works.

[simonbentley]

Optical character recognition software - as used in scanners - depends upon the ability to compare a pattern to a series of known letters (or parts of a letter).  The intentional 'waves' and 'cross hatches' that are used in the image render this impossible.  As a comparison, imagine if you took a pen and scribbles around the MICR characters on the bottom of a cheque - that would render the reading impossible by computer.

Contrary to your instincts, the 'copy the word' element is a remarkably secure technique which, to date, has foiled all attempts to break it.

[ursula62]

I believe the "copy the word" (or in some cases a number) part is to make sure that it is a human being completing the form rather than a bot.

[dafyd]

In fact these CAPTCHAs (their proper name) are actually broken fairly frequently, but not in the way you might expect...

By copying the image and presenting it as a Captcha on a bogus �free porn� web site. An unsuspecting human solves the problem for them, and the spammers return the answer to the original site. There are no shortage of people seeking free porn, so it�s done very quickly.

[slimfandango]

wow. that's pretty amazing. i hate pornographers on the net, but hats off to them this time. that's genius.

[simonbentley]

Not sure if the crack described is as easy as you think....the original site randomises the combination of letetr and numbers so how do you know that when a Human cracks it, you will be able to use that at the original site?

I doubt you could do it in realtime, most of the sites that use these timeout to prevent the 'try all combination' crackers.