Introduction - If you have any usage issues, please Google them yourself
TcpDump the " head" of the transmission of data packets in the network can be completely intercepted off providing analysis. It supports filtering for network layer protocol, host, network, or port, and to provide and, or, not a logical statement to help you get rid of useless information. tcpdump is a free network analysis tools, in particular, provided the source code, open interfaces, and therefore has strong scalability, are useful tools for network maintenance and intruders. tcpdump exist in the basic FreeBSD system, because it requires the network interface into promiscuous mode, normal users can not run properly, but users with root privileges can be executed directly on the network to get information. System network analysis tools are not a threat to the safety of the machine, but the other computers on the network security threats.