Packet sniffer’s, are protocol analyzers meant to capture the packets that are seen by a machine’s network interface. When a sniffer runs on a system, it grabs all the packets that come into and goes out of the Network Interface Card (NIC) of the machine on which the sniffer is installed. This means that, if the NIC is set to the promiscuous mode, then it will receive all the packets sent to the network if that network is connected by a hub. Fortunately, in a switched network, since switches do not broadcast the packets, sniffers cannot see any packet that is not having the destination address of the machine on which it is installed. A network analyzer can be a standalone hardware device with specialized software, or software that is installed on a desktop or laptop computer. Network analyzer is a tool, and like all tools, it can be used for both good and bad purposes.