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A packet analyzer (also known as a network analyzer, protocol analyzer or sniffer, or for particular types of networks, an Ethernet sniffer or wireless sniffer) is computer software or computer hardware that can intercept and log traffic passing over a digital network or part of a network.[1] As data streams flow across the network, the sniffer captures each packet and, if needed, decodes and analyzes its content according to the appropriate RFC or other specifications.



On wired broadcast LANs, depending on the network structure (hub or switch), one can capture traffic on all or just parts of the network from a single machine within the network; however, there are some methods to avoid traffic narrowing by switches to gain access to traffic from other systems on the network (e.g. ARP spoofing). For network monitoring purposes it may also be desirable to monitor all data packets in a LAN by using a network switch with a so-called monitoring port, whose purpose is to mirror all packets passing through all ports of the switch. When systems (computers) are connected to a switch port.

On wireless LANs, one can capture traffic on a particular channel.

On wired broadcast and wireless LANs, to capture traffic other than unicast traffic sent to the machine running the sniffer software, multicast traffic sent to a multicast group to which that machine is listening, and broadcast traffic, the network adapter being used to capture the traffic must be put into promiscuous mode; some sniffers support this, others don't. On wireless LANs, even if the adapter is in promiscuous mode, packets not for the service set for which the adapter is configured will usually be ignored. To see those packets, the adapter must be in monitor mode.


The versatility of packet sniffers means they can be used to:

  • Analyze network problems
  • Detect network intrusion attempts
  • Gain information for effecting a network intrusion
  • Monitor network usage
  • Gather and report network statistics
  • Filter suspect content from network traffic
  • Spy on other network users and collect sensitive information such as passwords (depending on any content encryption methods which may be in use)
  • Reverse engineer proprietary protocols used over the network
  • Debug client/server communications
  • Debug network protocol implementations

Notable packet analyzers

See also


  1. ^ Kevin J. Connolly (2003). Law of Internet Security and Privacy. Aspen Publishers. pp. 131. ISBN 978-0735542730.  

External links

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