4 ms·

I was wondering this. Surely a captcha needs to have some form of 'hidden knowledge' that is validated only by sending something to the server for it to check -

I was wondering this. Surely a captcha needs to have some form of 'hidden knowledge' that is validated only by sending something to the server for it to check - like the jigsaw puzzle captcha at the end of the article, or a 'pick the images containing a bus' kind of thing. With the slider, there doesn't appear to be anything stopping a bot client from just submitting a form and pretending that it interacted with some HTML and javascript.

ivanhoe 7y ago
It's just not popular enough to be handled by bot scripts (yet)... and most of spam bots are not targeting one particular site so this worked for a while, just like math captcha and drag-an-image worked for a while. The moment they get popular enough for bot authors to tackle the issue, they'll stop working.