Nmap

Nmap is a network discovery and security auditing tool. Use it only against systems you own or are explicitly authorised to test. The examples use 192.0.2.10, a documentation-only address from RFC 5737.

Authorisation required

Scanning someone else’s infrastructure without permission can be unlawful and disruptive.

Basic scan

Discover hosts and common services on a target:

nmap 192.0.2.10

Service detection

Probe discovered services for version information:

nmap -sV 192.0.2.10

All-port scan

Scan all TCP ports on a target (this can take longer and create more traffic):

nmap -p- 192.0.2.10

Common options

Option	Purpose
-sV	Probe for service versions
-p-	Scan ports 1–65535
-Pn	Treat host as online (when discovery is blocked)
-oN file.txt	Save normal output to a file

Example output

PORT   STATE SERVICE VERSION
22/tcp open  ssh     OpenSSH 9.6
80/tcp open  http    nginx