What Is Nmap?

Learn what Nmap can do.

We'll cover the following

Nmap is an open-source command-line tool that helps us map an entire network of devices. Gordon Lyon (pseudonym Fyodor) wrote Nmap as a tool to help system administrators map an entire network. If you are a sysadmin or do anything related to networking, chances are you’ve heard about Nmap.

What can Nmap do?

Nmap, a versatile network scanning tool, allows for detailed exploration of devices connected to a network, such as a home router with Wi-Fi. This process involves scanning various devices, ranging from computers and mobile phones to printers, connected to the router. The scan yields comprehensive information, including details of open ports, active services, versions of these services, operating systems in use, and potential vulnerabilities.

These vulnerabilities, once identified, can be avenues for gaining unauthorized access to these devices. This aspect of Nmap highlights its significance in both network security assessment and potential exploitation scenarios. The tool’s utility is not limited to standalone operations; it seamlessly integrates with other notable cybersecurity tools like Metasploit and Nessus.

In a typical scenario, if the IP address of a network is known, Nmap can be deployed to scan this network. The data acquired from Nmap scans is rich in insights and can be crucial for subsequent phases of network analysis or penetration testing. For instance, in an exploitation phase, results from an Nmap scan can be exported and effectively loaded into Metasploit. This integration facilitates a more streamlined and efficient approach to network security assessment, allowing for a combination of reconnaissance (via Nmap) and exploitation (via Metasploit).

Such capabilities underline the importance of Nmap in cybersecurity. It serves not just as a tool for identifying and analyzing network components and their vulnerabilities but also as a bridge that connects various stages and tools within the broader cybersecurity workflow. This interconnectivity enhances the effectiveness of security assessments and penetration testing exercises, making Nmap a fundamental tool in the arsenals of network security professionals.

Help command

Let’s try Nmap. We’ll look at the help command offered by Nmap, which lists all the commands that we can use with Nmap. This will come in handy during our pen testing engagements.

Start the terminal and run the following command:

nmap -h
Nmap help command
Terminal 1

We can see that Nmap lists all the commands, including a few examples of running scans. This will be a great reference for us if we get stuck while running a scan.