nmap, the network mapper, is a very powerful security scanner originally written by Gordon Lyon. It’s a tool that everyone who works in IT should be familiar with, not just security professionals. We want to help both promote its use and help you understand how to get the most out of it. If you’re new to nmap or have been using it in a simple way to look at hosts on your network, we hope there’ll be something you can learn here. If you have any specific requests, please get in touch. Basic nmap capabilities:

• Port scanning – find out what ports are open on specific hosts
• Host discovery – work out all the hosts within a given range/subnet
• OS detection – nmap will try to work out what OS a given host is running
• Service version detection – discover what version of a particular service is running
• NSE – the nmap scripting engine can interrogate hosts for a variety of outcomes

nmap is an immensely powerful tool that can help you understand the topology of your network as well as enumerate security risks that you may not have been aware of.