To block visitors from your site, create a .htaccess file and add the following
code (changing the IP's to reflect your requirements) - each command on
one line each:
order allow,deny
deny from 123.45.6.7
deny from 012.34.5.
allow from all
You can deny access based upon IP address or an IP block. The above blocks
access to the site from 123.45.6.7, and from any sub domain under the IP block
012.34.5. (012.34.5.1, 012.34.5.2, 012.34.5.3 etc)
Note: You can also set an option for deny from all, which would of course deny everyone.
You can also allow or deny by domain name rather than IP address.