Duo Security is a vendor of cloud-based two-factor authentication services. If you have an account with Duo it is easy to integrate Duo's two-factor authentication into your Auth0 application.
Click the link below that most fits your role to learn more:
Duo Security for Administrators - this page explains how to setup using Duo, how to reset accounts and how to disable using Duo.
Duo Security for Developers - this page explains how to enable using Duo for two-factor auth and details on how to configure it to meet your needs.
Duo Security for Users - this page is for users logging into your application using Duo. It also has troubleshooting tips for any issues they may encounter.