Aug 101998

nmap – the port scanner

This has to be the easiest port I’ve ever installed!  Or is it just that I’m getting to know how to do it?

Port scanner?  What’s a port scanner?

A port scanner doesn’t check for software.  Don’t confuse this with a FreeBSD port.

A port scanner checks the [service] ports on a host to see what services the host is willing to provide.  For example, SMTP, HTTP, etc.  It is a common method to find out what can be exploited on that host.  Using a port scanner is a good way to find out is turned on/off for a particular host.  You can also use it to help verify that your firewall restrictions are what you think they are.

Which scanner?

I chose to install nmap as found in the FreeBSD Security ports.  Don’t forget the nmap homepage.

The software can be downloaded from

The install

Well, I followed the instructions found in the FreeBSD handbook for compiling ports from the internet.  And it ran.  First time.

To get you started, try issuing the following command:

nmap -v localhost

That should show you all the ports available on your machine.