It's anecdotal, but since I added a little "What's two plus two" input
box to my forms, we hardly get any more form spam.  You could easily
switch the question each time, although I haven't had the need to.

We weren't getting hit once a minute, mind you, so you might be
attracting a better class of bots . . . .

On Tue, Jul 1, 2008 at 10:36 AM, MJ Ray <[log in to unmask]> wrote:
> Thomas Dowling <[log in to unmask]> wrote:
>> Does anyone know anything concrete about "cognitive" captchas?  I've run
>> into anecdotal support for things like:
>>    Enter the word "orange" <input name="foo">
> [...]
>> Are these known to work?  Or are they just clever guesses about what
>> bots might not be able to figure out?
>
> There are mostly anecdotes because this stuff is hard to test
> properly.  I found they worked a little, but are just clever guesses.
>
> "3.1 Logic puzzles
>
> The goal of visual verification is to separate human from machine. One
> reasonable way to do this is to test for logic. Simple mathematical
> word puzzles, trivia, and the like may raise the bar for robots, at
> least to the point where using them is more attractive elsewhere.
>
> Problems: Users with cognitive disabilities may still have trouble.
> Answers may need to be handled flexibly, if they require free-form
> text. A system would have to maintain a vast number of questions, or
> shift them around programmatically, in order to keep spiders from
> capturing them all. This approach is also subject to defeat by human
> operators."
>
> Source: http://www.w3.org/TR/turingtest/#logic
>
>
> As that last phrase hints, bots are not the only problem.  See
> http://www.schneier.com/blog/archives/2007/11/spammers_using.html
> for example.
>
>
> Hope that helps,
> --
> MJ Ray (slef)
> Webmaster for hire, statistician and online shop builder for a small
> worker cooperative http://www.ttllp.co.uk/ http://mjr.towers.org.uk/
> (Notice http://mjr.towers.org.uk/email.html) tel:+44-844-4437-237
>



-- 
Andrew Darby
Web Services Librarian
Ithaca College Library
http://www.ithaca.edu/library/
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