This is captcha module provide a web interface for human verification during registration.
Registration is carried out by invitation code. The code must be specified in advance in the plugin settings and the invitation code can be changed at any time through the admin panel.
This plugin is suitable for sites where you need to control user registration personally. Not public registrations.
Customize your invitation code and message to users.
4. All now the user, following your instructions, will be able to receive an invitation code and register on the site.
To prevent code brute force, set IP limits in the admin panel
More information: https://www.question2answer.org/