Awesoft

The “IP Whitelist” plugin allows administrators to limit access to the WordPress dashboard by whitelisting specific IP addresses. It’s intended to enhance security by restricting access to only trusted sources.

IP Whitelist

Allows administrators to limit access to the WordPress dashboard

Anthony

This plugin will limit access to the site. Only visitors with a cookie token will be able to access the public website. Visitors without the cookie will see a “coming soon” style of page.
You can customise the “coming soon” content, and you can change the way tokens work. Visit yoursite.com/?add_token to receive the token allowing you to see the site. To remove the limited access, simply disable this plugin.
By default, the token is “letmein”. So use these links: 
site.com?letmein 
site.com?takemeoff
This plugin is useful when you’re developing your site. You can work on your live web server without having your site open to the public.

Token Access

Limit access to the site to those with a cookie token.  Visitors without the cookie see a customisable "coming soon" style of page.

IP Whitelist vs Token Access