Nmap - what is it and how does it work?

Image of Stefan Thelberg
Stefan Thelberg

January 29, 2021

Nmap can be a solution to the problem of identifying activity on a network as it scans the entire system and makes a map of every part of it.

A common issue with internet systems is that they are too complicated for the ordinary person to understand. Even a small home-based system is extremely complex. When it comes to larger companies and agencies that deal with hundreds or even thousands of computers on the network, that complexity grows exponentially.

To learn which ports are open and what those rules are, a program called Nmap can be used. This program scans the network that a computer is connected to and outputs a list of ports, device names, operating systems, and several other identifiers that help the user understand the details behind their connection status.

Nmap can be used by hackers to gain access to uncontrolled ports on a system. All a hacker would need to do to successfully get into a targeted system would be to run Nmap on that system, look for vulnerabilities, and figure out how to exploit them. Hackers aren’t the only people who use the software platform, however. IT security companies often use it as a way to replicate the kinds of attacks that a system could potentially face.

How does it work?

Nmap works by checking a network for hosts and services. Once found, the software platform sends information to those hosts and services which then respond. Nmap reads and interprets the response that comes back and uses the information to create a map of the network. The map that is created includes detailed information on what each port is doing and who (or what) is using it, how the hosts are connecting, what is and is not making it through the firewall, and listing any security issues that come up.

How is all of that accomplished? Nmap utilizes a complex system of scripts that communicate with every part of the network. The scripts act as communication tools between the network components and their human users. The scripts that Nmap uses are capable of vulnerability detection, backdoor detection, vulnerability exploitation, and network discovery. Nmap is an extremely powerful piece of software, but there does tend to be a good deal of background knowledge required to use it correctly.

Internet security companies can use Nmap to scan a system and understand what weaknesses exist that a hacker could potentially exploit. As the program is open-source and free, it is one of the more common tools used for scanning networks for open ports and other weaknesses. At Holm Security, we use this technology in a very effective way, as we provide an excellent web-based security service, which ensures that the clients’ ports remain securely closed to those not granted permission.


Whether you are a private user with important information on your system, a major corporation or a government agency protecting a wealth of highly sensitive data, Nmap can provide the level of knowledge and pre-emptive thought required to keep things safe.

Holm Security VMP picture cta