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Testing for Captcha (OWASP-AT-012)

Revision as of 00:13, 18 November 2013 by Wilder (talk | contribs) (WARNING: Captcha protection is considered to be an ineffective security mechanism!)

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This article is part of the new OWASP Testing Guide v4.
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WARNING: Captcha protection is considered to be an ineffective security mechanism!

Most current used Captcha images can be easily cracked in a fully automated way using many commercial or opensource services. Commercial services are usually very cheap and provide a simple API for most programming languages.
It is not recommended to use Captcha protection for security-critical applications, in this case it is more suitable to use SMS text messages or OTP tokens instead.
Example of Google reCAPTCHA cracked in 7 seconds by commercial automated cracking service:
Price: US¢1.390
Uploaded: Sun Nov 17 20:03:13 2013
Solved: Sun Nov 17 20:03:23 2013
Text: 270 35524452

Brief Summary

CAPTCHA ("Completely Automated Public Turing test to tell Computers and Humans Apart") is a type of challenge-response test used by many web applications to ensure that the response is not generated by a computer.

Description of the Issue Short Description of the Issue: Topic and Explanation

Black Box testing and example

Testing for Topic X vulnerabilities:
Result Expected: