How to use Activity Monitor to view Network activity

My Activity Monitor is showing that something is downloading, I can the download activity on the graph and the overall speed is shown as 'Data received/sec. But I'm stuck trying to figure out which process it is that's using the network? I can sort by 'Rcvd Bytes' or 'Rcvd Packets', but those would seem to be cumulative totals. Isn't there some kind of '% Network' column??