A simple nmap tutorial for you..

[Sentinel]

I thought that I would write a small nmap tutorial for you so that you know how to do a thorough port scan on your own Linux dedicated server to check if there are any services running that you don't want.

So, there are two basic scan types

nmap -sS

nmap -sT

The -sS option will perform a syn scan
The -sT will perform a TCP (connect) scan

There are more advanced scans to try but they are out-with the scope of this tutorial =)

So, to get a port scan running on your own machine, simply issue one of the above commands with 127.0.0.1 as the host, eg

nmap -sS 127.0.0.1

nmap will output something like this

Starting Nmap 4.01 at 2006-07-06 17:23 BST
Interesting ports on chaos (127.0.0.1):
(The 1668 ports scanned but not shown below are in state: closed)
PORT     STATE SERVICE
21/tcp   open  ftp
22/tcp   open  ssh

Nmap finished: 1 IP address (1 host up) scanned in 0.207 seconds

This will show you the services that nmap found. It's up to you to figure out if you want to keep the services running, or to close them down.

Good luck.

[php_rules]

nmap is a fantastic tool, but it doesn't always give you the name of the service that's running, in cases where you find a random port number that's open you might want to check wikipedia's list of port numbers to find out the service that's running on that port.

[Amelia]

Helpful link.. Thanks!