NMAP, which stands for Network Mapper, is a free and open-source utility for network discovery and security auditing. It was originally designed to scan large networks, but it can work equally well for single hosts. Numerous systems and network administrators rely on Nmap for network inventory, managing service upgrade schedules, monitoring host or service uptime, and many other tasks. The tool uses different types of packets and reads the responses it obtains to discover hosts and services on a computer network, yielding information about those devices including the operating system they are running, what type of packet filters/firewalls are in use, what services (application name and version) are they offering to the visiting systems, and so on (Source: NMAP official website).
The most popular feature of NMAP is its ability to identify, the target system’s active hosts. An active host is a system that is operative and connected to the network. It is crucial to identify these to understand how many systems are connected to your network at any given time. NMAP does this through a process called Ping Scanning or ICMP Echo Request.
Nmap executes on all major computer operating systems, and both console and graphical versions are available. Nmap is flexible; it can adapt its behavior based on network conditions to optimize scan speed and accuracy. It also carries out aggressive scanning techniques to detect hosts that would reject less aggressive probes. In less controlled situations, Nmap can utilize slow, stealthy probes to evade detection by intrusion detection systems.
One of the significant characteristics of Nmap is its ability to provide a very detailed report of a network it has scanned. It identifies all the active hosts in the network and provides information on all the services each host is offering, the firewalls and filters they are using, it can sometimes even detect the type and version of the operating system a particular host is running (Source: Wikipedia).
Nmap supports a large number of scanning techniques such as SYN scan, ACK scan, TCP Open, Reverse Ident, FTP bounce, ICMP, FIN, and Push and Urgent Flag. Each of them is designed for a specific purpose and applies distinct methods to interact with the target (Source: NMAP official documentation).
In conclusion, Nmap is a very powerful and indispensable tool for network management, security auditing, and robust system administration. Despite its complexity, it has a well-organized and user-friendly interface that makes it an integral part of every security professional’s toolkit.
Sources :
1. NMAP official website. https://nmap.org/book/man.html.
2. Wikipedia page on NMAP. https://en.wikipedia.org/wiki/Nmap.
3. NMAP official documentation. https://nmap.org/book/man.html.
