网络嗅探器在网路安全方面扮演很重要的角色。使用网络嗅探器可以把网卡设置为混杂模式，并可实现对网络上传输的数据包的捕获与分析。次分析结果可供网络安全分析之用，更有可能被用来做一些黑客行为。本文将详细介绍嗅探器的实现原理，并给出一个简单的实例。(Network sniffer plays a very important role in network security. The network sniffer can be used to set the network card as promiscuous mode, and it can capture and analyze the data packets transmitted on the network. The results of sub analysis can be used for network security analysis, and more likely to be used to do some hacker behavior. In this paper, the implementation principle of sniffer is introduced in detail, and a simple example is given.)