Re^3: If CAPTCHA isn't the answer. What is?

It's been a while since I read the article, but I would assume that you are presented with a new set of pictures after an incorrect guess. With a large enough DB to avoid repeats I think your averages are way, way off.

But yes, of course hammering is to be avoided. There are other tools for that, like my module CGI::Application::Plugin::RateLimiter for example.

-sam

Comment on Re^3: If CAPTCHA isn't the answer. What is?

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Re^4: If CAPTCHA isn't the answer. What is? by ikegami (Patriarch) on Aug 02, 2006 at 04:49 UTC
The size of the database doesn't matter. With a small database size, you could actually do much better than the odds I gave as time goes on by remembering which images are known cats. I was talking straight brute force. For example, you could always select the top three squares. It doesn't matter how many gazillion of images are in the database, your chances of the three cats being in the top three squares are 1 in 84 (assuming the selection of the squares is random). Selecting three random squares instead of the top three squares does not change the math.	[reply]
Re^5: If CAPTCHA isn't the answer. What is? by Hue-Bond (Priest) on Aug 02, 2006 at 09:26 UTC
Than can be easily prevented by requiring that the user selects not "The three cats among these 9 images" but "All cats among these images" (there can be more or less, even none!) or maybe "The second brown cat and the last dog". -- David Serrano	[reply]
Re^6: If CAPTCHA isn't the answer. What is? by ikegami (Patriarch) on Aug 02, 2006 at 17:17 UTC
Indeed `1/10 * C(9,0) + 1/10 * C(9,1) + 1/10 * C(9,2) + 1/10 * C(9,3) + 1/10 * C(9,4) + 1/10 * C(9,5) + 1/10 * C(9,6) + 1/10 * C(9,7) + 1/10 * C(9,8) + 1/10 * C(9,9) = 1/10 * 2 * (1 + 9 + 36 + 336 + 4536) = 983.6` [download] 1 in 84 becomes 1 in 983.6 On the other hand, it makes it harder on the user. People will be second guessing themselves.	[reply] [d/l]