How to Prevent Spammer
To prevent spamer, you may try this methods
1. Change the /register/ slug to something unique. An example would be /create-your-account/, or something of that nature. It just needs to be unique and also make sense in a URL for your user. Spammers targeting BuddyPress look for /register/ as the signup page. It’s all automated so you want to filter them out at the first step.
2. Please try install and activate these plugins
3. Change your “Admin” username to something dificult and at least 10 characters (+) but easily to remember (+ for you – for security) or you have to read a note (-) safely secured in your safe locker (+)
4. Set recaptcha on Youzify Registration Form
5. Set Login attempt on Youzify Login page
However, checking Groups dashboard on your WP admin daily will keep being an important thing to do. You need to remove the Groups that created by bot and delete users that create it.