In Management Studio's Activity Monitor, (Current Activity > Process Info if using Enterprise Manager on SQL2000), there's a column labeled Net Address. One source I found says its the host's MAC address, though this doesn't seem right, as currently my three connections are represented with two different Net Addresses. Books Online says it's an:
Assigned unique identifier for the network interface card on each user's workstation. When the user logs in, this identifier is inserted in the Network Address column.
Is this some value that SQL Server assigns to a connection, or can I trace it back to a specific machine on the network (in this case, the Host field is empty)?