How to stop hackers from registering on sitte

Check out some plugins, for example: https://www.ads-software.com/plugins/stop-spammer-registrations-plugin/ https://www.ads-software.com/plugins/registration-honeypot/
https://www.ads-software.com/plugins/bad-behavior/ https://www.ads-software.com/plugins/cookies-for-comments/ https://www.ads-software.com/plugins/spam-free-wordpress/

In the admin area you can set it up so all new registrations must be manually approved by you. I do this but rather than deleting them, I ban their iP, email address and … I set it up so if they manager to slip by and get approved, all posts and comments must be approved. It’s a little more work but worth it. I go one step further and lodge complaints with their host. I lastly notify the company they are spamming.

There are sites that tell you who their host is, if it’s a hacked connection, what you send/copy and even provide cover letters.

Some spammers make $1,000/day. The company they represent won’t like spammers. You’ll cut them off at the knees plus keep your site a little cleaner.