Completely Automated Public Turing test to tell Computers and Humans Apart used in form validation to restrict access to humans only

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3
votes
4answers
792 views

Can a CSRF CAPTCHA be defeated?

One defense that developers use to protect against a CSRF attack is to implement a CAPTCHA in critical steps. A CAPTCHA ensures that a human is at the keyboard approving the activity. But I've ...
2
votes
5answers
859 views

Anyone using Asirra in production? Are there similar alternatives?

The Asirra project is a Captcha alternative that shows you pictures of kittens and puppies to fend off bots and prove that the end user is a human. Is anyone using Asirra (or something similar) in ...
8
votes
11answers
4k views

Is there a true alternative to using CAPTCHA images?

Security is about balancing costs and risks, nothing is impossible to beat, specially not typical CAPTCHA implementations, but they do add something no other system seems to offer. I've been reading ...
20
votes
3answers
1k views

If we know CAPTCHA can be beat, why are we still using them?

If we know CAPTCHA can be beat, why are we still using them? A 35% to 90% success rate like wikipedia is stating means software is better at solving CAPTCHAs then I am.
6
votes
4answers
3k views

Why Do we Need CAPTCHA? In what case we should use it?

In what case we should implement Captcha based security?. How accurate it is and if there exists any alternatives for Captcha based Security.
5
votes
5answers
1k views

How does CAPTCHA mitigate DDoS attacks?

This seems like an easy question, but I've failed to find an answer. One of the uses of CAPTCHA is to cope mitigate Denial of Service attacks. Suppose an adversary performs excessive login attempts, ...
5
votes
5answers
478 views

Why re-verify with CAPTCHA on failed form entry?

Is there a reason for sites to ask for another CAPTCHA verification when some other part of the registration form, e.g. the username, was invalid?