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 like network inventory, managing services upgrade schedules, and monitoring host or service uptime. Nmap uses raw IP packets in novel ways to determine that what host are available on the network, what service those hosts are offering, what OS they’re using, what variety of packet filters/firewalls are in use and dozens of other characteristics. It had been designed to rapidly scan large networks, but works fine against the single host. Nmap runs on all major computer OS and officially binary packages are available for Linux, Windows, and Mac OS.

Gordon Lyon (also known by his pseudonym Fyodor Vaskovich) is a network security expert. Lyon created Nmap, and has written numerous books.He is a founding member of the Honeynet Project and was Vice President of Computer Professionals for Social Responsibility.

To install Nmap in your Linux OS

type: sudo apt -get nmap

or you can visit https://nmap.org/ to install.

type: nmap -sP [IP range]

-sP: to scan ping

If you don’t know your IP address type: ifconfig and copy your IP address.

scanning IP 127.0.0.1

type: nmap -sS -A [Target]

sS: used for port scanning.

-A: used for OS version detection.

Port Scanning and OS version detection.

port scanning of Google.com

In the above screenshot you can see port 80/tcp and 443/tcp are an open port of Google.com and 998 are filtered ports (protected by a firewall).

TCP: Transmission control protocol.

UDP: User datagram protocol.

Type: nmap -p 0–65535 -sV -O -sS -T4 162.210.102.212

-p: to scan port between 0 to 65535.

-sV: to scan the Service version.

-O: for OS detection.

I hope you liked my short and simple article and learned a lot on port scanning which is the basics for information gathering and also the initial step to start the hack.

It is the most powerful tool to scan the ports of the target.