What Nmap Actually Does
Nmap sends packets and listens for what comes back. What comes back tells you more about a network than most administrators know about their own infrastructure. Gordon Lyon released Nmap in 1997 in a Phrack magazine article. It has been in active development since then and has appeared in over a dozen films, including The Matrix Reloaded, Die Hard 4.0, and Bourne Ultimatum, because filmmakers use it when they need a terminal to look like actual hacking. It is one of the most widely used security tools in existence, and most people who run it do not fully understand what it is doing. ...