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Nmap - What Is It & How Does It Work?

What Nmap is used for? 

Nmap, also known as Network Mapper, is a highly effective and adaptable network scanning tool. Its primary purpose is to explore networks and perform security audits. With Nmap, users can effortlessly discover hosts and services on a computer network, detect operating systems, identify open ports, and collect information about different network devices.

Common Use Cases For Nmap

  • Network Discovery: Nmap can scan an entire network or a range of IP addresses to identify active hosts available on the network.
  • Port Scanning: Nmap can scan target hosts to determine which ports are open, closed, or filtered. This information is valuable for assessing the security posture of a network and identifying potential vulnerabilities.
  • Service Version Detection: Nmap can probe open ports to determine the version and type of services running on those ports. This helps in identifying specific software versions and potential vulnerabilities associated with them.
  • Operating System Detection: Nmap can analyze network responses to identify the operating systems running on remote hosts. This information is helpful for network administrators to understand the composition of their network and implement appropriate security measures.
  • Scripting and Automation: Nmap provides a scripting engine (NSE - Nmap Scripting Engine) that allows users to write custom scripts to automate various network scanning tasks and perform specialized security checks.
Nmap is a widely used tool by network administrators, security professionals, and ethical hackers for network mapping, vulnerability assessment, and network security auditing.

If you want to know which ports are open and the corresponding rules, you can use Nmap. This program scans the network your computer is connected to and provides a list of ports, device names, operating systems, and other identifiers to help you understand your connection status. 

However, hackers can also use Nmap to access uncontrolled ports on a system. They can run Nmap on a targeted approach, identify vulnerabilities, and exploit them. But Nmap is not only used by hackers - IT security companies also use it to simulate potential attacks that a system may 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.

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