ICMP (Internet Control Message Protocol) is a protocol used within the internet protocol suite. Ping scans, also known as ICMP echo requests, are used in network diagnostics for scanning to primary determine whether or not the network is reachable. Network Mapper (NMAP) is a powerful tool for network discovery and security auditing. It sends specially crafted packets to the target host and then analyzes the responses.
However, there might be situations where you might want to make your scans less detectable by hiding ICMP pings when using NMAP. By default, NMAP uses an ICMP echo request to ping hosts before scanning them, but it’s possible to disable this in order to make your scan less noticeable.
To avoid sending ICMP ping requests, you can use the `-Pn` option while performing an NMAP scan. The `-Pn` option allows the NMAP scan to proceed without a preliminary pinging of the target host, thus lessening the likelihood of detection.
Here’s an example:
`nmap -Pn
However, bear in mind that there’s a trade-off here. Because using `-Pn` skips the host discovery phase and assumes the host is online, scanning times can be significantly increased. Therefore, it’s best used when you’re reasonably confident that the host is up and reachable.
If you still want to use some form of host discovery but minimize the chance of detection, NMAP provides several other methods for host discovery. For instance, you can combine the `-PS` option with the `-PE` and `-PA` options to use a TCP SYN ping, ICMP echo ping, and TCP ACK ping, respectively. This type of hybrid approach can sometimes be more effective at stealthily identifying hosts.
Example:
`nmap -PS80,443 -PE -PA80,443
In essence, hide ICMP pings when using NMAP involves carefully choosing and combining the different host discovery options provided by NMAP, based on the specifics of the network you’re scanning and your own detection risk tolerance.
The primary source of this information is the official NMAP documentation, which provides comprehensive guidance on the many options available with this versatile tool:
- NMAP. (2021). Host Discovery (“Ping Scanning”). https://nmap.org/book/man-host-discovery.html
- NMAP. (2021). NMAP Manual. https://nmap.org/book/man.html
For additional information on network scanning techniques and best practices, the following resources could be useful:
- Graham, R. (2001). FAQ: Network Intrusion Detection Systems. https://robertgraham.com/pubs/network-intrusion-detection.html
- Lyon, G. F. (2008). Nmap Network Scanning: The Official Nmap Project Guide to Network Discovery and Security Scanning. https://nmap.org/book/toc.html.
