Questions tagged [captcha]

Captcha is a type of challenge-response test used in computing as an attempt to ensure that the response is given by a human being and not generated by a computer.

CAPTCHA is an acronym for "Completely Automated Public Turing test to tell Computers and Humans Apart".

A CAPTCHA or Captcha is a type of challenge-response test used in computing as an attempt to ensure that the response is not generated by a computer. The process usually involves one computer (a server) asking a user to complete a simple test which the computer is able to generate and grade.

Because other computers are supposedly unable to solve the CAPTCHA, any user entering a correct solution is presumed to be human. Thus, it is sometimes described as a reverse Turing test, because it is administered by a machine and targeted to a human, in contrast to the standard Turing test that is typically administered by a human and targeted to a machine.

The usual reason for using a CAPTCHA is to prevent automated spam from being posted into a public discussion forum or similar site.

A common type of CAPTCHA requires the user to type letters or digits from a distorted image that appears on the screen. However these are becoming increasing unreliable as the automated spam systems that they are trying to defeat are becoming much better at reading the distorted text. More advanced CAPTCHAs are thus becoming available that require the user to answer more detailed questions or perform more complex actions.

Most CAPTCHAs, particularly the more difficult ones, suffer from accessibility issues. The act of making it difficult for an automated system to read and respond to the CAPTCHA also makes it more difficult for many users with disabilities to access sites that use them. For example, a user who relies on a screen reading web browser may be unable to see the CAPTCHA image. Better CAPTCHA systems will provide solutions to some of these issues, such as an audio alternative, but these users are generally still left at a disadvantage.

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Recommendations for a captcha on Ruby on Rails

I'd like to implement a captcha in a Rails project for a form submission, but I'm not sure what to go with. I'm inclining towards simplicity of implemention, and reliability when in use, over it being too sophisticated, as my application doesn't…
conspirisi
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When the bots attack!

What are some popular spam prevention methods besides CAPTCHA?
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Open Source Invisible reCAPTCHA alternatives

Is there any close or best open source solutions as Google's Invisible reCAPTCHA V2? And also as Google's regular reCAPTCHA V2(checkbox one)?
Payalord
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Stop spam without captcha

I want to stop spammers from using my site. But I find CAPTCHA very annoying. I am not just talking about the "type the text" type, but anything that requires the user to waste his time to prove himself human. What can I do here?
unreal
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New Google reCaptcha: How to change text "I'm not a robot"

I've installed the latest Google reCaptcha tool on our yoga website. Now the users are confused about the text "I'm not a robot" that appears next to the checkbox. Most of our users do not know what the word "robot" means in this context and they…
nu everest
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Best way to limit (and record) login attempts

Obviously some sort of mechanism for limiting login attempts is a security requisite. While I like the concept of an exponentially increasing time between attempts, what I'm not sure of storing the information. I'm also interested in alternative…
Elle H
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reCAPTCHA accepting one word out of two

I am a bit confused about how reCAPTCHA works. I have implemented it using ROR. Sometimes even if i specify only one word out of two, it returns true while sometimes it fails. I am really confused and not able to understand the behaviour…
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Cleaning up captcha image

I'm trying to clean up the image above I've tried several different methods using open cv, I either erode the original image too much to the point where parts of the letters become missing such as below: I'm not really sure sure how to get rid of…
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Detect when reCaptcha does not load

What is the best way to detect if a reCaptcha v2 does not load? I would like to alert users when they need to use the captcha to continue, but it was unable to load.
Matt
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Difference between CAPTCHA and reCAPTCHA

What are the differences between CAPTCHA and reCAPTCHA? What is the best situation to opt for reCAPTCHA?
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Is it immoral to put a captcha on a login form?

In a recent project I put a captcha test on a login form, in order to stop possible brute force attacks. The immediate reaction of other coworkers was a request to remove it, saying that it was inapropiate for that purpose, and that it was quite…
azkotoki
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How to deal with the captcha when doing Web Scraping in Puppeteer?

I'm using Puppeteer for Web Scraping and I have just noticed that sometimes, the website I'm trying to scrape asks for a captcha due to the amount of visits I'm doing from my computer. The captcha form looks like this one: So, I would need help…
user10021033
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Is there an Unobtrusive Captcha for web forms?

What is the best unobtrusive CAPTCHA for web forms? One that does not involve a UI, rather a non-UI Turing test. I have seen a simple example of a non UI CAPTCHA like the Nobot control from Microsoft. I am looking for a CAPTCHA that does not ask…
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How to Use Captcha in asp.net mvc

can any one tell me how to use captcha in asp.net mvc? is there any need to download any control for it?
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What is a good invisible captcha?

What is a good invisible captcha? My site requires JavaScript so anything which requires that is fine.
user34537