How to trace who's downloading in a network?

[prinsipe_ng_sablay]

Hello Guys,

Can you please suggest me any software that i can use to trace if somebody is downloading on the internet?
And if there's a software or tweaks i can do from the server to stop him from downloading or from the router?

Thank you in advance!

 

[qroon]

You can use this:

http://www.wireshark.org/