This (also known as Wireshark) is a fantastic open source network protocol analyzer for Unix and Windows.
It allows you to examine data from a live network or from a capture file on disk. You can interactively browse the capture data,
delving down into just the level of packet detail you need. Ethereal has several powerful features,
including a rich display filter language and the ability to view the reconstructed stream of a TCP session.
It also supports hundreds of protocols and media types.
Latest Release:- Wireshark 1.0.4 (Ethereal)
A powerful wireless sniffer. Kismet is a console based 802.11 layer2 wireless network detector, sniffer,
and intrusion detection system. It identifies networks by passively sniffing, and can even decloak hidden
networks if they are in use. It can automatically detect network IP blocks by sniffing TCP, UDP, ARP,
and DHCP packets, log traffic in Wireshark / TCPDump compatible format, and even plot detected networks
and estimated ranges on downloaded maps.
Latest Release:- Kismet-2008-05-R1
The classic sniffer for network monitoring and data acquisition. It is great for tracking down network problems or monitoring activity.
There is a separate Windows port named WinDump. TCPDump is the source of the Libpcap / WinPcap packet capture library.
Latest Release:- TCPDUMP 4.0.0
Ettercap is a terminal-based network sniffer/interceptor/logger for ethernet LANs.
It supports active and passive dissection of many protocols (even ciphered ones, like ssh and https).
Data injection in an established connection and filtering on the fly is also possible, keeping the connection synchronized.
Many sniffing modes were implemented to give you a powerful and complete sniffing suite.
Plugins are supported. It has the ability to check whether you are in a switched LAN or not,
and to use OS fingerprints (active or passive) to let you know the geometry of the LAN.
Latest Release:- Ettercap NG-0.7.3
A suite of powerful network auditing and penetration-testing tools.
This popular and well-engineered suite by Dug Song includes many tools. dsniff, filesnarf, mailsnarf, msgsnarf,
urlsnarf, and webspy passively monitor a network for interesting data (passwords, e-mail, files, etc.).
arpspoof, dnsspoof, and macof facilitate the interception of network traffic normally unavailable to an attacker
(e.g, due to layer-2 switching). sshmitm and webmitm implement active monkey-in-the-middle attacks against redirected ssh
and https sessions by exploiting weak bindings in ad-hoc PKI. Overall, this is a great toolset.
It handles pretty much all of your password sniffing needs.
Latest Release:- dsniff-2.3