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----- Original Message -----
From: "Benjamin Hawkes-Lewis" <bhawkeslewis@xxxxxxxxxxxxxx>
To: <access-uk@xxxxxxxxxxxxx>
Sent: Sunday, August 12, 2007 2:09 PM
Subject: [access-uk] Re: Graphical images - CAPTCHA
Adding an aural CAPTCHA certainly is an improvement. But the problem
with the CAPTCHA Project's claim that reCAPTCHA is accessible is that
even a combination of a visual CAPTCHA and an aural CAPTCHA is not
accessible to deafblind people. The typical alternative CAPTCHA
suggested for deafblind people is some form of simple written logic,
knowledge, or comprehension test:
http://www.w3.org/TR/turingtest/
However, the CAPTCHA Project claims that such tests would be trivial to
break. And even then, there's still the problem of trying to accomodate
people with learning disabilities.
> Meantime, I'd be interested to know if anyone here with
> their own web site has tried out CAPTCHA. Unfortunately I
> am having to consider it seriously myself due to robot
> attacks on our enquiry forms.
I haven't, but here's my two cents.
For small websites, I would implement alternatives to CAPTCHA first:
http://webaim.org/blog/2007/03/07/spam_free_accessible_forms/
Then I'd look into a simple text challenge-based system:
http://dmytry.pandromeda.com/texts/captcha_and_saptcha.html
If I found the spam volume was still too high for me to cope with, I
would consider implementing reCAPTCHA but only showing a CAPTCHA when a
form submission looks suspicious (the criteria for this would vary of
course). If the CAPTCHA is guarding a comment form, the ideal thing
would be allow the form to be submitted without the CAPTCHA, but send it
directly to the moderator rather than publishing. Also, always provide
an accessible email address so people can contact the webmaster for help.
I doubt reCAPTCHA is a sensible thing to implement as part of your
contact form. Just use decent a decent spam filter on your email
account. (e.g. I've found Gmail's filter pretty good.)
--
Benjamin Hawkes-Lewis
George Bell wrote:
A slight change of subject here for anyone encountering web
sites where signing up involves copying text from a graphic.
Doubtless there are others, but the original concept was
call "CAPTCHA" (for Completely Automated Turing Test To Tell
Computers and Humans Apart). A CAPTCHA is a program that
protects websites against bots by generating and grading
tests that humans can pass but current computer programs
cannot.
The official web site for this is at
http://www.captcha.net/. The software to do this is
actually free from this site, and I quote:-
"Get a Free CAPTCHA For Your Site
"A free, secure and accessible CAPTCHA implementation is
available from the reCAPTCHA project. Easy to install
plugins are available for WordPress, MediaWiki, PHP, Perl,
Python, and many other environments. reCAPTCHA also comes
with an audio test to ensure that blind users can freely
navigate your site."
Note that last sentence above, but please read on.
Now here's an extract from the same page concerning
"Guidelines".
"Guidelines
"If your website needs protection from abuse, it is
recommended that you use a CAPTCHA. There are many CAPTCHA
implementations, some better than others. The following
guidelines are strongly recommended for any CAPTCHA code:
"Accessibility. CAPTCHAs must be accessible. CAPTCHAs based
solely on reading text - or other visual-perception tasks -
prevent visually impaired users from accessing the protected
resource. Such CAPTCHAs may make a site incompatible with
Section 508 in the United States. Any implementation of a
CAPTCHA should allow blind users to get around the barrier,
for example, by permitting users to opt for an audio or
sound CAPTCHA."
Although they mention "Section 508", which applies to
American Law, it could equally apply in British law under
the DDA (Disability Discrimination Act).
So if you come across such sites where you do not have an
audible option, perhaps it might be worth taking the time
and trouble to refer the webmaster to
http://www.captcha.net/ and the Guidelines set down. If
they are an American organisation, they are definitely
breaking their own laws.
Meantime, I'd be interested to know if anyone here with
their own web site has tried out CAPTCHA. Unfortunately I
am having to consider it seriously myself due to robot
attacks on our enquiry forms.
George Bell.
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