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I believe, ettercap was a tool used a lot more often before things like wireshark and cain and abel came out or at least "got big".
It has support for a lot of different platforms, but it's main job is sniffiing the network and manipulating where the traffic goes or how it gets there thus allowing you to perform MiTM attacks easily. It features filtering just like wireshark and is able to dissect protocols just as well.