NMAP, also known as Network Mapper, is a versatile tool for network security scanning and discovery. With NMAP, you can audit a network for open ports, services and their versions, detect operating systems, and even detect vulnerabilities (Fyodor, 1997). The information below provides an overview of how to utilize NMAP for network vulnerability scanning.
First, you need to install NMAP. On a Linux system, you can often install NMAP using the package manager, for example, `sudo apt-get install nmap` for Ubuntu (NMAP.org). For windows users, you can download the software directly from the official NMAP website.
The initial step in scanning a network is understanding the network architecture by performing a ping scan using `-sn` option. This commands the software to ping all the devices within the specified IP range. The command would look like this: `nmap -sn 192.168.0.1-254`. The result of this command will list all devices, including their IP addresses, that are currently active within the network range.
Subsequently, you can perform a port scan to check for open ports. One of the most common scans used is the `SYN scan`, initiated by the `-sS` option. An example of this would be: `nmap -sS 192.168.0.1`.
Detecting the version of the services running can assist in finding known vulnerabilities. For this, you utilize the `-sV` flag, which instructs NMAP to determine the version of the service running on each open port. An example of how to use this feature would look like: `nmap -sV 192.168.0.1`.
Moreover, NMAP has scripts that you can use for advanced scanning. These scripts are coded in LUA and are present in the NMAP Scripting Engine (NSE). With over 600 scripts, you can do a multitude of things including vulnerability discovery. To use these scripts, you use the `—script` option and you can point it to specific discovery scripts or use wildcards. An example could be: `nmap -sV —script vuln 192.168.0.1` which would run all the scripts in the vuln category (NMAP.org).
Be aware, though, that accurate vulnerability scanning requires expert knowledge, and running a vulnerability scan doesn’t make your network safe per se. Furthermore, make sure that you have the appropriate permissions before scanning third-party networks, as without such permissions scanning can be considered illegal.
For more detailed information, the official NMAP book, ‘NMAP Network Scanning’ by Gordon Lyon, can serve as an excellent guide. It offers an in-depth understanding of how to use NMAP effectively for network security scanning.
Sources:
Lyon, G. Fyodor. (2008). NMAP Network Scanning: The Official Nmap Project Guide to Network Discovery and Security Scanning. https://nmap.org/book/man.html
NMAP. (n.d.). Nmap Documentation. https://nmap.org/docs.html.
