This document summarizes a research paper that examines packet sniffing. It discusses how packet sniffers work in both switched and non-switched networks. In non-switched networks, all nodes are connected to a hub, allowing packet sniffers to capture all traffic by putting the network card in promiscuous mode. In switched networks, packet sniffers can operate through techniques like ARP cache poisoning, CAM table flooding, and switch port stealing. The document also outlines positive applications of packet sniffing like network traffic analysis and intrusion detection.