Nmap (“Network Mapper”) tool is used in active reconnaissance in order to not only determine live systems but also determine the holes in systems. This versatile tool is one of the best tools in the hacking community and is well supported.

Installation

sudo apt-get install nmap

How to use

sudo nmap <target IP>

Examples

sudo nmap 10.11.0.1-100

Scan Techniques

TCP SYN port scan

nmap <target IP> -sS

TCP connect port scan

nmap <target IP> -sT

UDP port scan

nmap <target IP> -sU

TCP ACK port scan

nmap <target IP> -sA

TCP Window port scan

nmap <target IP> -sW

TCP Maimon port scan

nmap <target IP> -sM