Nmap, which stands for “Network Mapper,” is an open-source tool used for network discovery and security auditing. It can discover hosts and services on a computer network by sending packets and analyzing the responses. Among the various customization options provided by Nmap to enhance the accuracy and efficiency of network scanning, one notable option is “-PN.”
The “-PN” option is also known as the “no ping” option. According to the official Nmap documentation, this option tells Nmap not to do a ping before scanning ports. Normally, before Nmap starts to scan ports, it would first send an Internet Control Message Protocol (ICMP) echo request, more commonly referred to as a “ping,” to the target host. If the host responds to the ping, indicating it is alive, Nmap will proceed with port scanning. However, if there’s no response to the ping, Nmap assumes the host is down and will typically not scan the host’s ports.
Using the “-PN” option essentially skips the check to see if a host is up before scanning. The “-PN” option treats all hosts as if they are online and will scan their ports regardless of their response (or lack thereof) to an ICMP echo request.
The “-PN” option can be essential in various situations. For example, some network hosts may be configured to ignore ICMP echo requests due to firewall rules or because the network operator has disabled responses to pings. So, attempting to conduct a network scan without using the “-PN” option on such networks might result in an incomplete or incorrect view of the network.
Here is an example of using the “-PN” option: ‘nmap -PN 192.168.1.1’. This command tells Nmap to do a scan on the host at IP address “192.168.1.1” without first pinging it.
In the latest versions of Nmap, the “-PN” option has been replaced with the “-Pn” option, but they work in the same way.
It is important to remember that scanning networks without authorization is illegal in many locations. Nmap should only be used legally and responsibly.
References:
1. “Nmap Network Scanning” by Gordon Lyon, the official guide to the Nmap Security Scanner, a free and open source utility used by millions of people for network discovery, administration, and security auditing.
2. Official Nmap documentation: https://nmap.org/book/man-host-discovery.html
3. A helpful article “Nmap Cheat Sheet: From Discovery to Exploits” from Comparitech: https://www.comparitech.com/net-admin/nmap-cheat-sheet/
