https://secure.wphackedhelp.com/blog/whitelist-ip-address-wordpress/
In this post you will learn about:
Whitelist IP Address in WordPress
What Does Whitelisting IP Addresses Mean?
Why Whitelist IP addresses?
Benefits & Drawbacks Of Whitelisting IP Addresses
Whitelisting IP Address With Apache .htaccess
Whitelisting IP Addresses on Nginx Web Server
Using WordPress Plugins to Whitelist IP Address
Cerber Security
Anti-Spam by CleanTalk
Restricted Site Access plugin.
Security shield and firewall
How to Restrict WordPress Site Access by blocking IP address?
Blocking IP Addresses in WordPress via cPanel
Blocking IP Addresses in WordPress via plugins