I am facing a DDOS attack from a few hundred IP addresses, all of them coming from various cities in India and have the same organization: "................ for GPRS Service". (I'm not mentioning the whole name).

The attack started around 5 hours ago and it consists on hundreds of IP addresses that open 1 to 5 connections (as opposed to one or a few IPs making thousands of connections). The IP addresses are coming from a wide range of subnets.

Is there a way to tell the firewall to block the internet provider of the remote IPs, at least until the problem is solved?