L7 DDoS Profiles: CAPTCHA Settings


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

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



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



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. 


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


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)



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

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


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.
%DOSL7.captcha.image% %DOSL7.captcha.change%
<b>What code is in the image?</b>


Related Content


Was this article helpful?
2 out of 2 found this helpful
Have more questions? Submit a request