monitoring per-user traffic on my file server 2003

Is there a way to monitor data read and written to my server 2003 in real time, per AD user, and if possible, per file? We have 2003 AD server.

Something like Sessions and Open Files in Shared Folder Management (fs.mcs) but with data (read and written) for each user in in real time (like in the Networking tab in Windows Task Manager, or performance monitor)

The reason is that Bytes Received spikes on the network interface causes the server to freeze temporarily. I want to know which users are causing these spikes (don't worry, I won't be 'punishing' anyone).
If a GUI-based solution doesn't exist, I am fine with ASCII text output, as long as it illustrates the current usage.