这是一个监听网络的工具，不修改网络包。相对而言，防火墙看到所有网络包，它能屏蔽或者丢弃任何程序指定的包，而这个监听器只是检测显示和记录这些包。

一个强力的监听器是设置机器的网络适配器为“混杂模式”。网络适配器在混杂模式下收到的不仅是这个机器的数据包，而是所有物理链接上的包。-A "Packet Sniffer" is a utility that sniffs without modifying the network s packets in any way. By comparison, a firewall sees all of a computer s packet traffic as well, but it has the ability to block and drop any packets that its programming dictates. Packet sniffers merely watch, display, and log this traffic.



One disturbingly powerful aspect of packet sniffers is their ability to place the hosting machine s network adapter into "promiscuous mode." Network adapters running in promiscuous mode receive not only the data directed to the machine hosting the sniffing software, but also ALL of the traffic on the physically connected local network.