The dictionary definition of reconnaissance is military observation of a region to locate an enemy or ascertain strategic features. A good analogy for reconnaissance will be a thief studying the neighborhood to observe which houses are empty and which ones are occupied, the number of family members who live at the occupied houses, their entry points, the time during which these occupied houses are empty, and so on before he/she even thinks about stealing anything from that neighborhood.

Network reconnaissance relates to the act of gathering information about the target's network infrastructure, the devices that reside on the network, the platform used by such devices and the ports opened on them, to ultimately come up with a brief network diagram of devices and then plan the attack accordingly.

Next, we will detect such activities using Wireshark.