How Does a Packet Sniffer Work? In order to understand how a packet sniffer works, let’s take a step back and take a quick look at the basics of sending data over a network. In most computer networks, all traffic is ignored by a specific machine unless the communication is addressed to that machine. Though the data is directed at one machine, theoretically it can be accessed by many machines on the network.

Packet sniffers take advantage of this fact. A software packet sniffer commands the computer’s network interface card (NIC) to stop ignoring the traffic and start receiving communications from every computer on a network segment. With a packet sniffer, all data flowing through a network can potentially be accessed by unauthorized personnel.

Sniffing can be either filtered or unfiltered. Filtered sniffing will capture only specific data packets whereas unfiltered sniffing intercepts all data packets on the network.