Nmap is an open source network monitoring and port scanning tool to find the hosts and services in the computer by sending the packets to the target host for network discovery and security auditing.

Numerous frameworks and system admins additionally think that its helpful for assignments, for example, network inventory, overseeing administration overhaul timetables, and observing host or administration 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. it runs on all major computer operating systems, and official binary packages are available for Linux, Windows, and Mac OS X.

In addition to the classic command-line Nmap executable, the Nmap suite includes an advanced GUI and results in the viewer (Zenmap), a flexible data transfer, redirection, and debugging tool (Ncat), a utility for comparing scan results (Ndiff), and a packet generation and response analysis tool (Nping).

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Nmap is …

  • Flexible: Supports dozens of advanced techniques for mapping out networks filled with IP filters, firewalls, routers, and other obstacles. This includes many port scanning mechanisms (both TCP & UDP), OS detection, version detection, ping sweeps, and more. See the documentation page.
  • Powerful: Nmap has been used to scan huge networks of literally hundreds of thousands of machines.
  • Portable: Most operating systems are supported, including Linux, Microsoft Windows, FreeBSD, OpenBSD, Solaris, IRIX, Mac OS X, HP-UX, NetBSD, Sun OS, Amiga, and more.
  • Easy: While NMAP offers a rich set of advanced features for power users, you can start out as simply as “nmap -v -A targethost“. Both traditional command line and graphical (GUI) versions are available to suit your preference.
  • Free: The primary goals of this  NMAP Project is to help make the Internet a little more secure and to provide administrators/auditors/hackers with an advanced tool for exploring their networks. it is available for free download, and also comes with full source code that you may modify and redistribute under the terms of the license.
  • Well Documented: Significant effort has been put into comprehensive and up-to-date man pages, whitepapers, tutorials, and even a whole book! Find them in multiple languages here.
  • Supported: While it comes with no warranty, it is well supported by a vibrant community of developers and users. Most of this interaction occurs on the Nmap mailing lists. Most bug reports and questions should be sent to the nmap-dev list, but only after you read the guidelines.
  • Acclaimed: Nmap has won various honors, including “Information Security Product of the Year” by Linux Journal, Info World and Codetalker Digest. It has been included in many magazine articles, a few motion pictures, many books, and one comic book arrangement. Visit the press page for further subtleties.
  • Popular: Thousands of people download every day, and it is included with many operating systems (Redhat Linux, Debian Linux, Gentoo, FreeBSD, OpenBSD, etc). It is among the top ten (out of 30,000) programs at the Freshmeat.Net repository. This is important because it lends Nmap its vibrant development and user support communities.

1: To find out nmap version, run:  # nmap --version Sample outputs:

Nmap version 5.51 ( http://nmap.org ) 2: To scan an IP address or a host name (FQDN), run:  # nmap # nmap localhost # nmap 3:  Information out of the remote system:  # nmap -v -A scanme.nmap.org # nmap -v -A Sample outputs:  Starting Nmap 5.00 ( http://nmap.org ) at 2012-11-19 16:38 IST NSE: Loaded 30 scripts for scanning. Initiating ARP Ping Scan at 16:38 Scanning [1 port] Completed ARP Ping Scan at 16:38, 0.04s elapsed (1 total hosts) Initiating Parallel DNS resolution of 1 host. at 16:38 Completed Parallel DNS resolution of 1 host. at 16:38, 0.00s elapsed Initiating SYN Stealth Scan at 16:38 Scanning [1000 ports] Discovered open port 80/tcp on Discovered open port 22/tcp on Completed SYN Stealth Scan at 16:38, 0.27s elapsed (1000 total ports) 4:  Scan multiple IP address or subnet (IPv4):  nmap ## works with same subnet i.e. nmap,2,3 You can scan a range of IP address too: nmap You can scan a range of IP address using a wildcard: nmap 192.168.1.* Finally, you scan an entire subnet: nmap 5: Find out if a host/network is protected by a firewall:  nmap -sA nmap -sA server1.gbhackers.com 6: Turn on OS and version detection scanning script (IPv4):  nmap -A nmap -v -A nmap -A -iL /tmp/scanlist.txt  7:  Scan a host when protected by the firewall:  nmap -PN nmap -PN server1.gbhackers.com

8: Scan an IPv6 host/address: The -6 option enable IPv6 scanning. The syntax is:  nmap -6 IPv6-Address-Here nmap -6 server1.gbhackers.com nmap -6 2607:f0d0:1002:51::4 nmap -v A -6 2607:f0d0:1002:51::4 9:  How do I perform a fast scan:  nmap -F 10: Display the reason a port is in a particular state:  nmap --reason nmap --reason server1.gbhackers.com 11: Only show open (or possibly open) ports:

 nmap --open nmap --open server1.gbhackers.com 12: Show all packets sent and received:  nmap --packet-trace nmap --packet-trace server1.gbhackers.com

13: Show host interfaces and routes: This is useful for debugging (ip command or route command or netstat command like output using nmap)  nmap --iflist Sample outputs: Starting Nmap 5.00 ( http://nmap.org ) at 2012-11-27 02:01 IST ************************INTERFACES************************ DEV (SHORT) IP/MASK TYPE UP MAC lo (lo) loopback up eth0 (eth0) ethernet up B8:AC:6F:65:31:E5 vmnet1 (vmnet1) ethernet up 00:50:56:C0:00:01 vmnet8 (vmnet8) ethernet up 00:50:56:C0:00:08 ppp0 (ppp0) point2point up **************************ROUTES************************** DST/MASK DEV GATEWAY ppp0 eth0 eth0 vmnet1 vmnet8 eth0 ppp0 eth0 14: How do I scan specific ports:
 nmap -p [port] hostName ## Scan port 80  nmap -p 80 ## Scan TCP port 80
 nmap -p T:80 ## Scan UDP port 53 nmap -p U:53 ## Scan two ports ## nmap -p 80,443 ## Scan port ranges ##
 nmap -p 80-200 ## Combine all options ## nmap -p U:53,111,137,T:21-25,80,139,8080 nmap -p U:53,111,137,T:21-25,80,139,8080 server1.cyberciti.biz nmap -v -sU -sT -p U:53,111,137,T:21-25,80,139,8080 ## Scan all ports with * wildcard ## nmap -p "*" ## Scan top ports i.e. scan $number most common ports ## nmap --top-ports 5 nmap --top-ports 10 Sample outputs: Starting Nmap 5.00 ( http://nmap.org ) at 2012-11-27 01:23 IST Interesting ports on PORT STATE SERVICE 21/tcp closed ftp 22/tcp open ssh 23/tcp closed telnet 25/tcp closed smtp 80/tcp open http 110/tcp closed pop3 139/tcp closed netbios-ssn 443/tcp closed https 445/tcp closed microsoft-ds 3389/tcp closed ms-term-serv MAC Address: BC:AE:C5:C3:16:93 (Unknown) nmap done: 1 IP address (1 host up) scanned in 0.51 seconds


Nmap can perform various scanning operation and it has been leading scanning tool in the security industry since its release in 1997, also its worlds leading port scanners to find out open ports and firewall. still, Nmap used by various organizations and penetration tester to find out loops and secure the network.

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Also Read:

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Posted by Charlie