Nmap

Nmap (Network Mapper) is a command-line network scanner. Given hosts, ranges or CIDR blocks, it finds which machines are up, which ports are open, and what is listening on them. It is a standard tool for network inventory, auditing and security testing.

The common workflow builds up from simple to detailed scans. nmap 192.168.1.0/24 checks the most common ports across a subnet, -p picks ports, -sV probes open ports to identify service versions and -O attempts OS detection. -A turns on version detection, OS detection, default scripts and traceroute together. Several scan types are available, such as TCP connect and SYN scans, and some of them need root privileges.

The Nmap Scripting Engine (NSE) runs Lua scripts against targets for tasks like extra service enumeration and vulnerability checks; -sC runs the default set and --script selects others. Results can be written as normal text, XML or grepable output with -oN, -oX and -oG, which makes them easy to feed into other tools.

Running nmap with no arguments prints a summary of the most common options, and the man page and nmap.org documentation cover the rest. Zenmap is an optional graphical front-end. Only scan networks you own or have permission to test. The license is the Nmap Public Source License, which is free for end users, with a commercial license for redistribution in products.

Installation

# via Build from source
./configure
make
make install