nmap

Nmap (Network Mapper) is an open-source tool specialized in network exploration and security auditing, originally published by Gordon "Fyodor" Lyon. The official website ( http://nmap.org ) describes it as follows:

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.

There are many other port scanners out there, but none of them even comes close to offering the flexibility and advanced options of Nmap. The Nmap Scripting Engine (NSE) has revolutionized the possibilities of a port scanner
by allowing users to write scripts that perform custom tasks using the host information collected by Nmap.
Additionally, the Nmap Project includes other great tools:


Additionally, the Nmap Project includes other great tools:

1- Zenmap: A graphical interface for Nmap
2- Ndiff: A tool for scan result comparison
3- Nping: An excellent tool for packet generation and traffic analysis
4- Ncrack: An Nmap-compatible tool for brute forcing network logins
5- Ncat: A debugging utility to read and write data across network