http://localhost/drupal-cvs/admin/settings/ip-blocking
Current I can only block one single IP address. It will be great if drupal allows to block entire subnet by providing a CIRD notation
http://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing
eg : 192.0.2.96/24 - this will block all IP address in the range of 192.0.2.x