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    Response Processors: Request Captcha Processor: Incident - Unsupported Audio Captcha Requested

    Complexity: Medium (3.0)

    Default Response: 3x = Slow Connection 2-6 seconds for 1 day and Warn User. 5x = 1 Day Block.

    Cause: A captcha is a special technique used to differentiate between human users, and automated scripts. This is done through a Turing test, where the user is required to visually identify characters in a jumbled image and transcribe them into an input. If the user is unable to complete the challenge in a reasonable amount of time, they are not allowed to proceed with their original request. Because it is nearly impossible to script the deciphering of the image, automated scripts generally get stuck and cannot proceed. Additionally, an audio version is optionally available to allow users who have a visual handicap to complete the captcha successfully. Captchas are used in two different ways by the system. They can be explicitly added to any workflow within the protected web application (such as requiring a captcha to login, or checkout a shopping cart), and they can be used to test a suspicious user before allowing them to continue using the site (similar to blocking the user, but with a way for the user to unblock themselves if they can prove they are not an automated script). Captchas are generally used to resolve "Insufficient Anti-Automation" weaknesses in the protected web application. Regardless of which type of captcha is being used, this incident is generated when the user attempts to request the audio version of a captcha challenge when support for audio captchas has been explicitly disabled.

    Behavior: Solving an image based captcha is exceptionally difficult and requires a great deal of time and research. Solving an audio captcha however is far less difficult. There are already multiple open source libraries available for translating speech to text. As such, it is often necessary to disable the support of "audio" captchas for critical workflows (such as administrative login dialogs), unless absolutely necessary for accessibility reasons. This incident occurs when the audio captcha has been disabled, but a user is attempting to manually request the audio version of the captcha challenge anyway. The captcha interface does not expose a link to the audio version unless it is explicitly enabled in configuration, so this would require that the user knows where to look for the audio version, they understand the filename conventions, and they know how to make the request manually to download the file. In either case, if audio captchas are not enabled (through configuration), then this effort will not be successful.

    Published: 2015-02-04