Nmap is a network computer scanner that can look for various things on a computer it finds on the network, like OS type, ports open and programs/services/servers that use those ports, this is commonly used to find holes in your own network so you can do something about them, also people with nasty intent use it to find ways to do bad things, so it’s a double edged sword. Whatever you do, get permission from some appropriate organization/sysadmin in charge of something, they get feisty when nmap runs amok on the network, possibly for good reason.
|command||what it does|
|nmap -F -T5 -sS 220.127.116.11||scans for open ports on IP 18.104.22.168 (you could also do 22.214.171.124/24 to scan a whole 255.255.255.0 subnet for the same thing)|
|nmap -sS -sU -sR -P0 -A -v 126.96.36.199||scans for TCP (sS) UDP (sU) portmap (sR) with OS/version detection (A) info and prints our Verbose (v) output on the machine at 188.8.131.52. Make sure you have permission to run this on their machine, otherwise you won’t make any friends doing it 🙂|