Ever wondered how attackers know what ports are open on a system? Or how to find out what services a computer is running without just asking the site admin? You can do all this and more with a handy little tool called Nmap.
What is Nmap? Short for "network mapper," nmap is a veritable toolshed of functionality to perform network scans. It can be used for security scans, simply to identify what services a host is running, to "fingerprint" the operating system and applications on a host, the type of firewall a host is using, or to do a quick inventory of a local network. It is, in short, a very good tool to know.

It's famous, too. Once you get to know Nmap a bit, you'll notice that it makes all types of cameo appearances in movies.

In this tutorial, I'll cover some of the basics of using Nmap and provide some examples you can use quickly.

Getting Nmap and Basic Use

You'll find Nmap packaged for most major Linux distros. The most recent release of Nmap came out in early 2010, so the most recent version (5.21) might not be in the current stable releases. You can find the sources and some binaries on the download page.

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