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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11
votes
12answers
7k 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 ...
23
votes
3answers
2k 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.
8
votes
4answers
37k 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.
0
votes
1answer
466 views

Protect database resources from fake data inputs via web forms

Scenario: I'm working on a project that needs to accept large amounts of data (customer data) from its users. So it can be normal to have a user trying to add 10,000 or 100,000 records at a time. In ...
11
votes
7answers
4k 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
4answers
3k views

CAPTCHA or email confirmation?

I have read that captcha isn't a perfect solution to protect a website where for example the user can create an account, since there are many people in different countries that practicallty read ...
-5
votes
2answers
1k views

Is it possible to break captcha? [duplicate]

Possible Duplicate: Can a CSRF CAPTCHA be defeated? Is it to possible break captcha? If yes, how? If no, why websites use difficult captcha systems?
2
votes
2answers
161 views

Are these email captchas legitimate?

The last week, I've been getting this kind of emails to addresses that I don't use: Dear Sir, Madam, For security reasons and as part of our ongoing fight against spam, it is our policy not ...
1
vote
1answer
372 views

How reliable/secure is QCaptcha?

QCaptcha is an alternative way to protect a website from bots. It required a drag and drop action like this: Question How reliable is this implementation when compared to others mentioned on ...
3
votes
4answers
2k 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 ...
5
votes
5answers
1k 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?
9
votes
7answers
1k views

What type of captcha will you recommend?

What type of captcha will you recommend? I am looking mainly at usability, ease of use (development too), relatively secure Usability I find that those captcha with very curly words/numbers are ...
2
votes
5answers
1k 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 ...