Wikipedia
A packet analyzer or packet sniffer is a computer program, or computer hardware such as a packet capture appliance, that can intercept and log traffic that passes over a computer network or part of a network Packet capture is the process of intercepting and logging traffic 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 A packet analyzer used for intercepting traffic on wireless networks is known as a wireless analyzer or WiFi analyzer
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