Note
	This document describes the very latest version of Nmap available fromhttps://nmap.org/download.html orhttps://nmap.org/dist/?C=M&O=D. Please ensure you are using the latest version before reporting that a feature doesn't work as described.

Nmap (“Network Mapper”) is an open source tool for network exploration and security auditing. It was designed to rapidly scan large networks, although it works fine against single hosts. 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. While Nmap is commonly used for security audits, many systems and network administrators find it useful for routine tasks such as network inventory, managing service upgrade schedules, and monitoring host or service uptime.

The output from Nmap is a list of scanned targets, with supplemental information on each depending on the options used. Key among that information is the“interesting ports table”. That table lists the port number and protocol, service name, and state. The state is eitheropen,filtered,closed, orunfiltered.Open means that an application on the target machine is listening for connections/packets on that port.Filtered means that a firewall, filter, or other network obstacle is blocking the port so that Nmap cannot tell whether it isopen orclosed.Closed ports have no application listening on them, though they could open up at any time. Ports are classified asunfiltered when they are responsive to Nmap's probes, but Nmap cannot determine whether they are open or closed. Nmap reports the state combinationsopen|filtered andclosed|filtered when it cannot determine which of the two states describe a port. The port table may also include software version details when version detection has been requested. When an IP protocol scan is requested (-sO), Nmap provides information on supported IP protocols rather than listening ports.

In addition to the interesting ports table, Nmap can provide further information on targets, including reverse DNS names, operating system guesses, device types, and MAC addresses.

A typical Nmap scan is shown inExample 15.1. The only Nmap arguments used in this example are-A, to enable OS and version detection, script scanning, and traceroute;-T4 for faster execution; and then the hostname.

#nmap -A -T4 scanme.nmap.orgNmap scan report for scanme.nmap.org (74.207.244.221)Host is up (0.029s latency).rDNS record for 74.207.244.221: li86-221.members.linode.comNot shown: 995 closed portsPORT     STATE    SERVICE     VERSION22/tcp   open     ssh         OpenSSH 5.3p1 Debian 3ubuntu7 (protocol 2.0)| ssh-hostkey: 1024 8d:60:f1:7c:ca:b7:3d:0a:d6:67:54:9d:69:d9:b9:dd (DSA)|_2048 79:f8:09:ac:d4:e2:32:42:10:49:d3:bd:20:82:85:ec (RSA)80/tcp   open     http        Apache httpd 2.2.14 ((Ubuntu))|_http-title: Go ahead and ScanMe!646/tcp  filtered ldp1720/tcp filtered H.323/Q.9319929/tcp open     nping-echo  Nping echoDevice type: general purposeRunning: Linux 2.6.XOS CPE: cpe:/o:linux:linux_kernel:2.6.39OS details: Linux 2.6.39Network Distance: 11 hopsService Info: OS: Linux; CPE: cpe:/o:linux:kernelTRACEROUTE (using port 53/tcp)HOP RTT      ADDRESS[Cut first 10 hops for brevity]11  17.65 ms li86-221.members.linode.com (74.207.244.221)Nmap done: 1 IP address (1 host up) scanned in 14.40 seconds

The newest version of Nmap can be obtained fromhttps://nmap.org. The newest version of this man pageis available athttps://nmap.org/book/man.html.It is also included as a chapter ofNmap Network Scanning: The Official Nmap Project Guide to Network Discovery and Security Scanning.