My site http://remotejobs.io currently uses a plugin to power the job board and user supplied resumes. The plugin creates users from it's own interface, so there is not typical user creation method on the site.
However, lately I've had an overwhelming amount of new user creations from spam bots. I know the difference because I get a new user registration email from these users who I suppose are just hitting the http://remotejobs.io/wp-login.php?action=register page, whereas the interface used by users actually posting a resume or a job doesn't generate this email notification.
Is there someway to block the ability for spam bots to create accounts this way without disabling user registration all together?
To be clear, no spam is actually ending up on the site because users can only post content through the plugin's interface. But I'd like to prevent a user database filled with spam accounts.
EDIT: I'm using the wpjobboard plugin.