Nmap (Network Mapper)
Used in port scanning, one of the phases in ethical hacking, is the finest hacking software ever. Primarily a command-line tool, it was then developed for operating systems based on Linux or Unix, and the windows version of Nmap is now available.Nmap is basically a network security mapper capable of discovering services and hosts on a network, thereby creating a network map. This software offers several features that help in probing computer networks, host discovery as well as detection of operating systems. Being script extensible it provides advanced vulnerability detection and can also adapt to network conditions such as congestion and latency while scanning.