Nmap a fundamental application in your linux system

Nmap is an open source program used to trace TCP and UDP ports. It is used to evaluate the security of computer systems, as well as to discover services or servers on a computer network. It is a very useful tool since it offers a lot of information both on the server machine and on other machines.

Before starting to install this utility, we will proceed to update the repositories

using the apt-get update command. This will update it when downloading by

package any program. It is written in the console:

sudo apt-get update

Now that the repositories are updated, we will proceed to download and install “nmap”

by parcel. By downloading a program by package, it is installed in the system automatically, which makes the apt-get tool / command become the great asset of this distribution.

Once downloaded and installed on the system, the way to run this program / service will be to write the nmap command accompanied by the domain name or IP address to the console. It is written in the console:

sudo apt-get install nmap nmap localhost

These are, then, the open ports for the "localhost" address, which is no other address than that of the server machine. These ports are obviously local, which means that not all of them need to be opened in a router in order to provide services to the Internet, although many of them do.

An example is 3306, which is open for Mysql, being this local, and not needing to be opened in the router. In contrast, port 80, open for the HTTP service, is local, and in addition, it must normally be opened in the router to be able to view web pages from the Internet to the server.

In summary; With this tool you can have control of the open ports on the server machine (and on other machines), and thus apply more security.