Sean Fisher

This plugin will hide WordPress Admin (/wp-admin/) when a user isn’t logged in. If a user isn’t logged in and they attempt to access WP Admin directly, they will be unable to and it will return a 404. It can also rename the login URL.
Also, you can add HTTP authentication directly from WP Admin and add custom username/password combinations for the HTTP auth or use the WordPress credentials.
This doesn’t touch any .htaccess files or change the WordPress core files. All the CSS/Images under /wp-admin/ are still accessible, just not the .php ones.
If you enable HTTP authentication, it will add HTTP authentication to the PHP files in /wp-admin/.
To contribute to the development, check out <a href="https://github.com/srtfisher/Lockdown-WPAdmin" rel="nofollow ugc">the GitHub Repository</a>.

Lockdown WP Admin

Lockdown WP Admin conceals the administration and login screen from intruders. It can hide WordPress Admin (/wp-admin/) and and login (/wp-login.

Justin Busa

This plugin allows you to hide the WordPress admin, login and signup pages from all users except those with a specific capability. Unauthorized users will be redirected via a 301 redirect to your site’s homepage or a URL that you specify in the settings.
This plugin is useful if you want to allow signups for your site but only want users with a certain capability (e.g. edit_others_pages for editor and administrator) to be able to access the admin area. This helps to ensure that malicious users can’t access something that you didn’t intend for them to access.
You are also given the option to redirect the WordPress login and signup pages to your own custom pages. Redirecting those pages in addition to the admin can also help secure your site from someone trying to attack those URLs.
Hidden WP Admin is brought to you by the fine folks at <a href="https://www.wpbeaverbuilder.com/?utm_source=external&utm_medium=wp-repo&utm_campaign=hidden-admin-description" rel="nofollow ugc">Beaver Builder</a>.

Hidden WP Admin

Hide the WordPress admin, login and signup pages from all users except those you allow.

Lockdown WP Admin vs Hidden WP Admin