Introduction

Network Mapper (Nmap) was originally released by Gordon Fyodor Lyon in the infamous Phrack magazine Vol 7 Issue 51 (https://nmap.org/p51-11.html). It is acclaimed today as one the best tools for network reconnaissance and security auditing in the information security industry. The first public version was introduced as an advanced port scanner along with a paper describing research on techniques for port discovery, but it has become so much more. It has evolved into an essential, fully featured tool that includes several other great subprojects, such as Ncrack, Ncat, Nping, Zenmap, and the Nmap Scripting Engine (all of them are available at https://nmap.org/). Nmap is described as follows in the official website:

"Nmap (Network Mapper) is a free and open source (license) utility for network discovery and security auditing. Many systems and network administrators also find it useful for tasks such as network inventory, managing service upgrade schedules, and monitoring host or service uptime. Nmap uses raw IP packets in novel ways to determine what hosts are available on the network, what services (application name and version) those hosts are offering, what operating systems (and OS versions) they are running, what type of packet filters/firewalls are in use, and dozens of other characteristics. It was designed to rapidly scan large networks, but works fine against single hosts. Nmap runs on all major computer operating systems, and official binary packages are available for Linux, Windows, and Mac OS X."

Other tools in the project were created to meet the specific needs of users. Nping (https://nmap.org/nping/) specializes in network packet crafting. Ncrack (https://nmap.org/ncrack/) focuses on network authentication cracking. Ncat (https://nmap.org/ncat/) is an enhanced version of Netcat and allows users to read, write, redirect, and modify network data. Zenmap (https://nmap.org/zenmap/) is a cross-platform GUI focused on usability. Finally, the Nmap Scripting Engine (https://nmap.org/book/nse.html) takes scanned information obtained from targets and provides an interface for users to script additional tasks.

Nmap's community is very active, so I encourage you to always keep up with the releases and latest patches. Announcements and discussions take place on the development mailing list, so if you would like to contribute to the project, I recommend you subscribe to it.

This first chapter is for newcomers. Starting with building Nmap, we will become familiar with all the tools of the Nmap project. In just a few recipes, you will learn how flexible and powerful Nmap really is, but as we move through chapters, we will go deep into the internals to learn not only how to use the tools but to extend them and create your own. The practical tasks chosen for this chapter will help you fingerprint local and remote systems, map networks, craft custom network packets, and even identify systems with weak passwords.