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L7 DDoS Profiles: CAPTCHA Settings

Description

When configuring L7 DDoS Profiles, CAPTCHA is one of the available mitigation actions.

See How to Configure New L7 DDoS Profiles for more details.

 

Environment

  • Silverline Portal
  • L7 DDoS Profiles v3 (updated in Jan 2020)
  • Proxy / Proxied customers

 

Procedure

CAPTCHA Settings 

1. Click "View CAPTCHA Settings" to configure CAPTCHA.

  • Profile must be in Blocking Mode to see the CAPTCHA Settings
  • Seconds (i.e. 120 seconds in image below) are the amount of time the client is allowed to attempt the CAPTCHAs before mitigation moves onto rate-limiting. 

Mitigation_Blocking_CAPTCHA_.png

2. In pop-up, configure the First Response Type and Failure Response type.

CAPTCHA_Wide.png

Response Type Description
First Response Type
  • First CAPTCHA presented to client when this detection mechanism triggers
  • By default, the CAPTCHA configuration page will display a basic CAPTCHA image (as shown).
  • Can instead select a Custom CAPTCHA (see next section)
Failure Response Type
  • Next CAPTCHA presented to client, if they fail to pass the First Response CAPTCHA.
  • The CAPTCHA challenge sequence will continue to be displayed if the client fails the test until the Time Allowed per Mitigation Level is exceeded 
  • Can instead select a Custom CAPTCHA (see next section)

 

Custom CAPTCHA

If you want to use a custom script, you can follow the instructions below.

1. From either Response Type drop-down, select Custom option.

Screen_Shot_2019-03-07_at_11.44.14_AM.png

2. Enter HTML with custom variables.

You can use the following variables within the challenge or response:

Variable Use
%DOSL7.captcha.image% Displays the CAPTCHA image in data URI format.
%DOSL7.captcha.change% Displays the change CAPTCHA challenge icon.
%DOSL7.captcha.solution% Displays the solution text box.
%DOSL7.captcha.submit% Displays the Submit button.

 

Example of Custom CAPTCHA:

This question is for testing whether you are a human visitor and to prevent automated spam submission.
<br>
%DOSL7.captcha.image% %DOSL7.captcha.change%
<br>
<b>What code is in the image?</b>
%DOSL7.captcha.solution%
<br>
%DOSL7.captcha.submit%

 

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