Date: 25.09.2022 - Category: Tutorial
Network Mapper, alias Nmap, is an open-source tool for network exploration and security auditing. You can use it to scan large networks pretty fast, but it also works against single hosts. Nmap sends raw IP packets to the target host to gather information and output the list of the scanned hosts. It will determine what services, operating systems, packet filters/firewalls, and dozens of other stuff are running on the scanned system.
To create a map of the target network, you have to scan it to list all active devices. To do that, you can use two different techniques:
To target a single or range of ports you can use the
To get more information about the scanned host, you can use the verbose output flag
That is useful to export nmap results to avoid redundant scans and monitor the step by step actions Nmap performs on a network.
Stealth scans complicate the detection of the scanning system for a target by not completing the 3-way handshake of a TCP connection.
It sends an SYN packet to the host. If an SYN/ACK packet is received, a port on the target is open, and you can open a TCP connection.
To perform a stealth scan, you have to use the flag
The downside of stealth scanning is that it is slower and not as aggressive as the other types of scanning.
Let's find the versions of applications with Nmap, which is a crucial part of penetration testing.
You can search for existing vulnerabilities in the Common Vulnerability and Exploits (CVE) database for the particular found version.
To scan a version of a service you can use the
But keep in mind, that the version scan is not always correct. But it will give you a good overview of the services on the scanned system.
Nmap can also provide information about the active operating system on the target host using TCP/IP fingerprints.
You can use the
-O flag to enable the operating system detection:
It is also possible to use the flag
-osscan-limit to limit the detection to promising targets. Nmap will show the probability of each operating system guess.
Like version scanning, the OS scan is not always accurate but can help to collect some information about the target.
But to get far better information than with regular scans, Nmap provides an aggressive mode. That enables OS and version detection, traceroute and script scanning.
-A will enable the aggressive scan:
However, aggressive scans will send more packets to the target host, which is easier detectable.
The Nmap Scripting Engine(short NSE) is a powerful tool write and automate scans.
To perform such a scan use the
You can find the location of all available NSE scripts using the locate util:
You can also use the list of NSE scripts on the nmap homepage:
List of Nmap Scripts
To peform a vulnerability scan, Nmap provides the powerful script category vuln. To allow Nmap to use the Vulners exploit database, pass the
-sV flag while using the NSE script: