An established premier packet analyzer
Pros & Cons:
Wireshark (formerly Ethereal) has established itself as the premier packet analyzer. It can capture packets of standard Ethernet, PPP and VPN interfaces.
I have used it many times to identify people running heavy reports bringing servers down to a crawl.
Wireshark requires installation of Windows Packet Capture package (WinPcap). WinPcap allows for other software to 'listen' secretly to the information coming and going through the network card on the computer. I found it better to install the latest WinPcap first, rather than versions included with the programs.
A portable version of Wireshark is available from the developer.
Wireshark was reviewed by Gizmos Freeware on