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The idea is explained here

In simple words, Nginx Proxy plays the role of load balance and transmits the HTTP/HTTPS requests to servers.

If the number of request times within a certain period from an individual IP exceeds a threshold, it will trigger a captcha for the upcoming requests.

And the end-user must input the correct captcha code before he can continue to access the site.

Do you know any open source / free NGINX module for this usage? I searched on the Internet and here is one of them: seems it needs modification.

Any suggestion / experience is welcome, thank you

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marked as duplicate by HopelessN00b Feb 18 '15 at 6:18

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

up vote 1 down vote accepted

I think, captcha will only annoy your real users. For this problem I'd rather use the testcookie-nginx-module.

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Thanks, I don't quite understand how it works from its sequence charts. Will it prevent Search Engine Crawler to parse my site? – Mr.Wang from Next Door Jul 5 '12 at 5:11
Well, it depends on your imagination mostly :) I guess that correct robots.txt file would be a better option to filter out search bots. In addition to this, you can use nginx rules - like this way. – hangover Jul 6 '12 at 4:50

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