Nmap – Utility for scanning open ports
nmap is a tool for scanning open ports on the server. Often, new users cannot find the error, thanks to which they cannot get to their server or any application that must have access to the Internet. It is also a good way to check, what ports do we have open, which we do not use and we can close (bots will use open ports to attack servers).
If you have not logged in to the root account, remember to sudo!
INSTALLATION
nmap is not normally installed on Ubuntu, to install it we make
1 | apt update |
for package updates, and
1 | apt install nmap |
for installing the tool itself. If the installation was successful, after entering the command
1 | nmap --version |
something like this should appear to us:
USE OF THE TOOL
The simplest use of this tool comes down to typing
nmap {ADDRESS IP}
At the very beginning we have information about it, that nmap starts working. Later we have a report about our target server: information on the number of closed ports (Not shown: 997 closed ports) and a list of open ports.
PORT – open port
STATE – here is information about whether the port is open – OPEN – or closed – CLOSE.
SERVICE – service information, which uses the port (for port 22 this is ssh, for 80 http a dla portu 3306 this is mysql)
At the end we see information about the completed scan, number of IP addresses and scan time.
My use of this tool is only basic use, we can e.g.. display information about the operating system used. I recommend that you familiarize yourself with the additional nmap functions by entering nmap or man nmap.
