*tcpdump* is a common packet analyzer that runs under the command line. It allows the user to display TCP/IP and other packets being transmitted or received over a network to which the computer is attached. Distributed under the BSD license, tcpdump is free software.
*Nmap*, short for Network Mapper, is a free, open-source tool for vulnerability scanning and network discovery. Network administrators use Nmap to identify what devices are running on their systems, discovering hosts that are available and the services they offer, finding open ports and detecting security risks.
**iptables** is a command line utility for configuring Linux kernel **firewall** implemented within the https://en.wikipedia.org/wiki/Netfilter[Netfilter] project. The term ''iptables'' is also commonly used to refer to this kernel-level firewall. It can be configured directly with iptables, or by using one of the many
***SSH Tunneling***, is the ability to use ssh to create a bi-directional encrypted network connection between machines over which data can be exchanged, typically TCP/IP.
