Tracing the Ip address in the network

Hello,
We are having a internet connection from the service provider and we shared it to all our apartment through a hub/switch. It seems someone is using torrent tools to download stuffs which is reducing the speed of the internet( i came to this conclusion because during the day time when all of us went out the internet speed is good, when at evening when all are back its too slow, sometimes not even loading the google search page). Is there any software that use most of the internet bandwidth or block the bandwidth to others? If there is anything like that is it possible to trace the ipaddress and name that computer which is using most of our connection bandwidth( i don't know the real technical terms of all of it). Also how can i see all the computers which is using that particular internet connection.

Any help in this will be appreciated greatly.

Thanks in advance...


regards

Anwer