Nmap (“Network Mapper”) is a free and open source utility for network discovery and security auditing. I along with many other systems and network administrators also find it to be a useful tool for the right job. Nmap can be installed and used in Windows, and mostly common in Linux distributions such as Debian and the well known Ubuntu.
You can get the Windows install form http://nmap.org/ along with the Linux versions. In Linux (Debian) I simple sudo apt-get install nmap -y and the rest is done in a few seconds.
Now that you have Nmap, what can you do? Here are some examples I use every so often:
~# nmap google.com – gives me info about google.com (Hostname google.com resolves to 11 IPs..)
~# nmap 192.168.1.0/24 – scans my network and return info on machines and service ports listening
~# nmap -sP 192.168.1.100 – attempts to detect if a host is up or down
~# nmap -PN 192.168.1.100 – attempts to detect if a host is up or down (no pings sent)
~# nmap -sT 192.168.1.100 – port scan using TCP
~# nmap -sU 192.168.1.100 – port scan using UDP
~# nmap -O 192.168.1.100 – attempts to identify the remote OS, returns TCP/IP fingerprint
And I could go on, but lets just end these example here and I’m sure you’ll find others.
Run … run, you clever boy … and remember. – Clara Oswald