SOLDIERX.COM Nobody Can Stop Information Insemination

Hi guys, I need some of you guys expertise help. A friend of mine business is ISP, the thing is I found out today that the network has been infected and also I found out there not a firewall. So there a lot of people using this ISP service and hooked up to it.

Here are the questions:

1 --How to find the infected PC's on this ISP network?
2--How to pinpoint where or/and which address it's coming from?
3--Can we stop it in the mean time from broadcasting anymore or infecting any more PCs on ISP network?
4-- How to prevent it again?
5--What is the best software to use to identify, prevent, etc...?
6--Any advice on this or even stuff I forgot to ask would greatly help.

Please ASAP THXS