Network traffic monitoring. (which IP makes big traffic?)

["Cho Yoonbae" <yoonbae@nate.com>]

Hi,

My network has been very slower than before.
Someone suspected the virus like nimda.

So I have to found out who makes very high traffic..
I am not network engineer now.

What things I have to know?
and Which softwares I can select?

I'm asking advice for you.
Have a nice day.

byebye