Introduction
Nmap (short for Network Mapper) is a free and open-source network scanner tool that is used to discover hosts and services on a computer network, and to determine what devices are running on the network and what services they are offering. It was developed by Gordon Lyon (also known as Fyodor Vaskovich).
Nmap is widely used by network administrators and security professionals to perform network discovery, security scans, and vulnerability assessment. It can be used to scan large networks with hundreds of thousands of devices, or small networks with just a few devices.
Nmap uses a variety of techniques to scan networks, including raw IP packets, TCP and UDP port scans, and application-level probes. It can identify the operating system and version of devices on the network, as well as the types of services and servers that are running on them.
Nmap is available for Linux, Windows, and MacOS, and can be run from a command-line interface or through a graphical user interface. It is a powerful and flexible tool that is widely used in the field of network security.
Nmap use cases
There are many use cases for Nmap, including:
Network discovery: Nmap can be used to scan a network and discover all the devices and services that are running on it. This is useful for:
Creating an inventory of all the devices and services on a network: By scanning a network with Nmap, it is possible to create a comprehensive inventory of all the devices and services that are running on the network. This can be useful for keeping track of all the assets on a network and for identifying any unauthorized devices or services.
Identifying rogue devices: Nmap can be used to scan a network and identify any devices that are not authorized to be on the network. This can include rogue access points, unauthorized servers, or other devices that may pose a security risk.
Identifying devices and services that are no longer in use: Nmap can be used to scan a network and identify devices and services that are no longer in use, or that have been decommissioned. This can help organizations to clean up their networks and remove unnecessary or outdated assets.
Maintaining an up-to-date network map: By regularly scanning a network with Nmap, it is possible to maintain an up-to-date map of the network and identify any changes or additions to the network. This can be useful for keeping track of network changes and ensuring that the network is properly configured and secure.
Security scanning: Nmap can be used to perform security scans to identify vulnerabilities on a network. This can include
Identifying open ports: Nmap can scan a network and identify all the open ports on the devices on the network. This can be useful for identifying services that are running on the network and for identifying any open ports that may be vulnerable to attack
Identifying the operating systems and services running on devices: Nmap can be used to identify the operating systems and services running on devices on a network. This can be useful for identifying any outdated or unpatched systems, or for identifying services that may be vulnerable to attack.
Identifying misconfigured or unpatched systems: Nmap can be used to scan a network and identify any systems that are misconfigured or unpatched. This can help organizations to prioritize their efforts to secure their networks and protect against potential threats.
Performing network-wide security assessments: Nmap can be used to perform security assessments on an entire network, identifying potential vulnerabilities and security risks. This can be useful for organizations that need to ensure that their networks are secure and compliant with industry standards.
Identifying potential attack vectors: By scanning a network with Nmap, it is possible to identify potential attack vectors that could be exploited by malicious actors. This can help organizations to identify and address potential security weaknesses before they are exploited.
Vulnerability assessment: Nmap can be used to identify vulnerabilities on a network, such as open ports, unpatched systems, and misconfigured services. This can help organizations to prioritize their efforts to secure their networks and protect against potential threats.
Identifying open ports: Nmap can scan a network and identify all the open ports on the devices on the network. This can be useful for identifying services that are running on the network and for identifying any open ports that may be vulnerable to attack.
Identifying the operating systems and services running on devices: Nmap can be used to identify the operating systems and services running on devices on a network. This can be useful for identifying any outdated or unpatched systems, or for identifying services that may be vulnerable to attack.
Identifying misconfigured or unpatched systems: Nmap can be used to scan a network and identify any systems that are misconfigured or unpatched. This can help organizations to prioritize their efforts to secure their networks and protect against potential threats.
Performing network-wide vulnerability assessments: Nmap can be used to perform vulnerability assessments on an entire network, identifying potential vulnerabilities and security risks. This can be useful for organizations that need to ensure that their networks are secure and compliant with industry standards.
Identifying potential attack vectors: By scanning a network with Nmap, it is possible to identify potential attack vectors that could be exploited by malicious actors. This can help organizations to identify and address potential security weaknesses before they are exploited.
Network mapping: Nmap can be used to create a map of a network, showing the relationships between devices and services. This can be useful for visualizing the network and identifying potential vulnerabilities or bottlenecks.
Creating a visual representation of a network: By scanning a network with Nmap and creating a map of the network, it is possible to get a visual representation of the network and see how the devices and services are connected. This can be useful for understanding the layout and structure of a network, and for identifying potential vulnerabilities or bottlenecks.
Identifying network dependencies: By creating a map of a network with Nmap, it is possible to identify the dependencies between different devices and services on the network. This can be useful for understanding how a network functions and for identifying potential points of failure.
Identifying potential bottlenecks: By creating a map of a network with Nmap, it is possible to identify potential bottlenecks on the network, such as devices or services that may be overburdened or underperforming. This can be useful for identifying and addressing potential performance issues on a network.
Troubleshooting network issues: By creating a map of a network with Nmap, it is possible to identify potential issues on the network and troubleshoot them more effectively. For example, if a device or service is experiencing performance issues, it may be possible to identify the cause of the issue by examining the network map and identifying any dependencies or bottlenecks on the network.
Planning network expansions: By creating a map of a network with Nmap, it is possible to plan for future expansions of the network and identify any potential issues that may arise as a result of the expansion. This can be useful for organizations that are planning to grow their networks or add new devices or services to the network.
Penetration testing: Nmap can be used as part of a penetration test to identify vulnerabilities and potential attack vectors on a network. This can help organizations to identify and address potential security weaknesses before they are exploited by malicious actors.
Nmap scripting engine
Nmap (Network Mapper) includes a scripting engine (NSE) that allows users to write and run custom scripts to automate various tasks. These scripts are organized into categories based on their function. Some of the categories available in the NSE include:
auth: Scripts that are designed to perform authentication-related tasks, such as password cracking or testing for weak passwords. Example: "ssh-brute" (brute-forces SSH login credentials)
broadcast: Scripts that are designed to scan broadcast networks and gather information about the hosts that are connected to them. Example: "smb-enum-shares" (enumerates shared SMB resources)
brute: Scripts that are designed to perform brute-force attacks, such as guessing passwords or trying to guess login credentials. Example: "http-form-brute" (brute-forces HTTP login forms)
default: Scripts that are included with Nmap and are run by default when no specific scripts are specified. Example: "dns-recursion" (tests for DNS recursion)
discovery: Scripts that are designed to gather information about hosts and networks, such as identifying the operating system, open ports, and running services. Example: "smb-os-discovery" (determines the operating system of an SMB host)
dos: Scripts that are designed to perform denial-of-service (DoS) attacks. Example: "udp-flood" (floods a target with UDP packets)
exploit: Scripts that are designed to exploit vulnerabilities or vulnerabilities. Example: "ms08-067-netapi" (exploits a vulnerability in the Windows operating system)
fingerprint: Scripts that are designed to identify the operating system or other characteristics of a host or network. Example: "ssl-cert" (identifies the SSL certificate of a service)
safe: Scripts that are designed to be safe to run and are unlikely to cause harm to the target host or network. Example: "http-headers" (retrieves HTTP headers from a web server)
vuln: Scripts that are designed to identify known vulnerabilities. Example: "ssl-heartbleed" (tests for the Heartbleed vulnerability in SSL)
To run a script from a specific category, users can use the "--script" option followed by the category name and a "*" wildcard. For example, the following command will run all of the scripts in the "discovery" category:
Nmap -- script=discovery* 192.168.0.1
Users can also specify multiple categories by separating them with a comma. For example, the following command will run all of the scripts in the "discovery" and "vuln" categories:
Nmap -- script=discovery*,vuln* 192.168.0.1
These are just a few examples of the many categories and scripts available in the NSE. There are hundreds of scripts available, covering a wide range of functions and use cases.
