Sniffing is a method in which we monitors and analyzes network traffic, it’s occasionally used for a program that analyze data other than network traffic.
Cain & Abel:
Cain & Abel is a password recovery tool for Microsoft Operating Systems. It allows easy recovery of various kind of passwords by sniffing the network, cracking encrypted passwords using Dictionary, Brute-Force and Cryptanalysis attacks, recording VoIP conversations, decoding scrambled passwords, recovering wireless network keys, revealing password boxes, uncovering cached passwords and analyzing routing protocols.
Wireshark is the world’s foremost network protocol analyzer. It’s mostly used for capturing a network packets.
Ettercap is a comprehensive suite for man in the middle attacks. It features sniffing of live connections, content filtering on the fly and many other interesting tricks. It supports active and passive dissection of many protocols and includes many features for network and host analysis.