NMAP, also known as Network Mapper, is a free and open-source network scanning tool used by administrators to discover, diagnose, and analyze network systems. It is renowned for its precision in detecting open ports. However, as with any other system, its results might be influenced by several variables.
NMAP’s precision depends heavily on the scanned system’s configuration, complexity, and the security measures in place. Firewalls, intrusion prevention systems (IPS), or network address translation (NAT) can occasionally confuse or block NMAP scans, leading to inaccurate results (O’Farrell,Amol. “Nmap Tutorial: from the Basics to Advanced Tips.” Guru99, www.guru99.com/nmap-tutorial.html). Additionally, remote systems that limit incomplete TCP traffic may impact the reliability of the TCP SYN scan, a method commonly used by NMAP (Lyon, Gordon. “Port Scanning Techniques.” Nmap Network Scanning, nmap.org/book/man-port-scanning-techniques.html).
That being said, NMAP possesses superior features that are known for increasing accuracy. With its numerous scanning options, including the TCP SYN, Connect(), UDP, and others, and its Host detection feature, NMAP offers high flexibility and customization when it comes to the scanning process. This flexibility plays a key role in enhancing the tool’s accuracy (Fyodor. “Nmap Free Security Scanner.” Nmap: the Network Mapper, nmap.org).
A notable research study demonstrating the accuracy of NMAP is the one conducted by A. Farquharson (2006). By running NMAP against several test devices and comparing the open/closed/filtered port lists, he showed that the results were 90-100% accurate (Farquharson, Andrew. “NMAP 4 Network Exploration and Security Auditing.” HumanOriented, www.humanoriented.com/projects/recent-publications/nmap-4-network-exploration-and-security-auditing).
Another academic research by the Savonia University of Applied Sciences used NMAP to scan various systems while comparing its results with other scanning tools. This study stated that NMAP was not only accurate but performed faster than the other tools.
However, it should be noted that NMAP scans are not completely foolproof and are subject to false positives and negatives. A false positive occurs when NMAP identifies a port as open, but it is actually closed, and vice versa for a false negative. This can be due to several factors including rate restrictions, firewall policies, unstable network conditions, or simply an oversight in the tool’s configuration (PenTest-Tools. “Port Scanner– Detect Open Ports of a Given Target Host.” www.pentest-tools.com/network-vulnerability-scanning/tcp-port-scanner-online-nmap).
To conclude, the accuracy of NMAP in detecting open ports is generally high and reliable, provided the intricacies of the network and the scanning techniques are well understood and correctly applied.
