Those are SPAM guys so you can avoid by using below tips.
- Enable recaptcha plugin for registration and posting Q/A. This plugin is not enabled on your site.
- If you still see SPAM users then enable moderation for users.
- Also enable moderation for all posts.
- change permissions for posting question or answer. set users with 150 points can post. This will filter all SPAM.
Let me know if you still see issue.