Nmap, also known as Network Mapper, is an open-source tool utilized for network exploration or security auditing. Able to identify hosts on a network, scan for open ports or services, and recognize the operating system a host is using, Nmap is an integral resource in a network analyst’s toolkit.
To initiate a network analysis using Nmap, two core components need to be identified: the target and the type of scan. The target can range from a single hostname, an IP address, or an entire network. Scans range in complexity from rudimentary ‘ping’ scans to more intricate scans like the SYN scan or service version scan (Michael, 2016).
Perhaps most commonly, Nmap is used to generate a basic inventory of a network. To do this, a simple ping scan (also known as a network sweep) can be employed. The command used to perform a network sweep is “nmap -sn [target network]” where the target network can be in the form of “192.168.1.0/24”. This command will return a list of ‘up’ or ‘down’ hosts on the target network (Nmap.org, n.d.).
To execute a more comprehensive examination of the network environment, a SYN scan can be implemented. This scan checks each potential TCP port on each host in the network to see if the port is open. This is accomplished by running the command “nmap -sS [target network]”. The scan will return a list of open, closed, or filtered ports for each host (Michael, 2016).
Finally, Nmap provides the opportunity to determine the version of services running on open ports using a service version scan. The command “nmap -sV [target host]” can be used. This command returns a detailed list of services, running versions, and potentially extra information depending on the service (Nmap.org, n.d.).
It is worth mentioning that while Nmap is a powerful tool, it needs to be used ethically and legally, taking into account laws around devices penetration and data handling under regulations, such as GDPR, HIPAA etc. Unauthorized scanning and probing can lead to legal trouble.
To sum up, through a combination of these scans (among others), Nmap serves as an effective tool for network analysis. Its versatility renders it capable of adapting to the user’s unique network exploration needs.
Sources:
Michael, C. (2016). Network Attacks: Tools of the Trade. Sans Institute Reading Room. https://www.sans.org/reading-room/whitepapers/threats/network-attacks-tools-trade-37637
Nmap.org. (n.d.). Nmap Documentation. https://nmap.org/docs.html.
