If your webserver is Apache, you may block access to your website from specific IP addresses using .htaccess file.
You need to create this file in your document root folder and add these example lines:
order allow,deny deny from 127.0.0.1 allow from all
These lines will block access for all users using 127.0.0.1 IP address.
If you need to block a group of IP addresses. use these example lines:
order allow,deny deny from 127.0.0.1/24 allow from all
These lines will block access for all IP addresses within the 127.0.0.1/24 subnet. This should be in CIDR notation.