A Flarum extension.
Checks new user registrations against the StopForumSpam database. If either the confidence or frequency thresholds are reached, the user is prevented from completing their registration on your forum. SSO register via fof/oauth and fof/passport is also supported. Other SSO providers should work, but are untested.
Install with composer:
composer require fof/stopforumspam:"*"composer update fof/stopforumspamAn extension by FriendsOfFlarum.