嗅探（Sniffers）是一种黑客的窃听手段，一般是指使用嗅探器对数据流的数据截获与封包分析（Packet analysis）。

• 分析网络问题
• 分析网络信息流通量
• 探测企图入侵网络的攻击
• 探测由内部和外部的用户滥用网络资源
• 探测网络入侵后的影响
• 监测链接互联网宽频流量
• 监测网络使用流量（包括内部用户，外部用户和系统）
• 监测互联网和用户电脑的安全状态
• 获取帐号一般为管理员帐号与密码等机密信息
• 渗透与欺骗

A packet analyzer (also known as a network analyzer, protocol analyzer or packet sniffer—or, for particular types of networks, an Ethernet sniffer or wireless sniffer) is a computer program or piece of computer hardware that can intercept and log traffic that passes over a digital network or part of a network. As data streams flow across the network, the sniffer captures each packet and, if needed, decodes the packet's raw data, showing the values of various fields in the packet, and analyzes its content according to the appropriate RFC or other specifications.