QCaptcha is an alternative way to protect a website from bots. It required a drag and drop action like this:
How reliable is this implementation when compared to others mentioned on this site?
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Here's how QapTcha works:
However, it's relatively trivial to bypass - we just fake the functionality of QapTcha completely. First, we grab the HTML of the page. Then, we send a POST to the initialisation PHP script, containing the random value. Finally, we send the POST with the random empty field set. Bam!
This is somewhat of a security-through-obscurity captcha, because any bot that knows about it can bypass it. However, it's reasonably safe to assume that it'll stop most non-targeted "drive-by" attacks, until QapTcha is prevalent enough to be worth bot developers' time.