嗅探器通常是软硬件的结合。专用的嗅探器价格非常昂贵。另一方面，免费的嗅探器虽然不需要花什么钱，但得不到什么支持。

嗅探器与一般的键盘捕获程序不同。键盘捕获程序捕获在终端上输入的键值，而嗅探器则捕获真实的网络报文。嗅探器通过将其置身于网络接口来达到这个目的——例如将以太网卡设置成杂收模式。（为了理解杂收模式是怎么回事，先解释局域网是怎么工作的）。-Sniffer is usually a combination of hardware and software. Dedicated sniffer prices very expensive. On the other hand, although free sniffer does not need to spend any money, but very little support. General sniffer program to capture a different keyboard. Keyboard capture program to capture in the terminal input keys, and the sniffer will capture the true message of the network. Sniffer by its exposure to the network interface to achieve this objective- for example, Ethernet card set to miscellaneous collection mode. (In order to understand how miscellaneous collection mode is going on, first of all explain how the work of local area network).