Packet Sniffing
How Packet Sniffing Works

The computer running the packet sniffing software is required to be connected to the local area network you wish to eavesdrop on.
Packet sniffing in its simplest environment works best when its associated computer is connected through a hub.
When not connected through a hub but a switch, additionaly steps are needed to be performed to track the switch into behaving as a hub.
Packet sniffing simply acts as a probing device that captures data on the same network.
Although it is required to be on the same LAN, there are ways to work within that limitation.