NMAP(Port Chacker)


Vishal Vyas (Linux Admin)

Nmap With Example

NMAP is one of the most important tool. Which checks which ports are open on a machine.

Some important to note about NMAP

  1. NMAP abbreviation is network mapper
  2. NMAP is used to scan ports on a machine, either local or remote machine (just you require ip/hostname to scan).
  3. NMAP is can be installed on windows, Sun Solaris machines too.
  4. NMAP can be used to scan large networks, remember I am saying large networks.
  5. NMAP can be used to get operating system details, uptime, software used for a service and its version no, vender of network card and uptime of that system too(Don’t worry we will see all these things in this post.
  6. Please do not try to use NMAP on machines which you don’t have permission.
  7. Can be used by hackers to scan for systems for venerability.
  8. Just a funny note : You can see this NMAP used by trinity in Matrix-II, when she tries to hack in to electric grid super computer.

Note : NMAP man pages one of the best man pages I have come across. It is explained in such a way that even new user can understand it easily and one more thing it is even having examples in to how to use NMAP in different situations, when you have time read it. You will get lots of information.

Example1 : Using NMAP in normal way, i.e. to scan a particular system for open ports
#nmap hostname

Example2 : Scanning for a single port on a machine
#nmap –p 22 hostname
This will scan for 22 port is open on a host or not. And here –p indicates port.

Example3 : For scanning only ports
#nmap –F hostname
-F is for fast scan and this will not do any other scanning like IP address, hostname, operating system, and uptime etc. It’s very much fast as it said in man pages.

Example4 : For scanning only TCP ports
#nmap –sT hostname
Here s is for scanning and T is for only scanning of TCP ports

Example5 : For scanning only UDP ports
#nmap –sU hostname
Here U indicates UDP port scanning

Exmaple6 : Scanning for ports and to get what is the version of different services running on that machine
#nmap –sV hostname
V indicates version of each network service running on that host

Example7 : To check which protocol is supported by the remote machine
#nmap –sO hostname

Example8 : To scan a system for operating system and uptime details
# nmap -O hostname
-O
is for operating system scan along with default port scan

Example9 : Scanning a network
#nmap networkID/subnetmask
For the above command you can try in this way
#nmap 192.168.0.0/24

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