What is a port?

Important points

• It's associated with the IP address of the host.
• It's also associated with protocol type of the communication. Example: TCP, FTP, etc.
• It's identified with a 16 bit number. Example: 80

Using the NMAP Security Scanner

Some things to know about NMAP

• NMAP is open-source, so you can download the whole source code.
• NMAP is completely free to use.
• NMAP is not meant for malicious activities.

To get an overview of all the params that NMAP can be used with

>_ nmap -help 

To scan using hostname

>_ nmap <hostname>

To scan using IP Address

>_ nmap <ip address>

To scan using "-v" option

>_ nmap -v <host>

To scan multiple hosts at the same time

>_ nmap <host1> <host2> <host3>

To scan a whole subnet or IP range

>_ nmap 192.168.0.*

What is subnet?

A network divided into two or more networks is called subnet. 

To scan a list of hosts using a .txt file

>_ nmap -iL filename.txt

To scan an IP Address range

>_ nmap 192.168.0.101-105

To scan OS information

>_ nmap -A <host>

To enable OS detection with NMAP

>_ nmap -o <host>

To scan a host to detect firewall

>_ nmap -sA <host>

To scan a host to see if it's protected by any packet filtering software or firewalls.

>_nmap -PN <host>

Find live hosts in a network

>_ nmap -sP 192.168.0.*

To scan for a specific port

>_ nmap -p 80 <host>

To scan for multiple ports

>_ nmap -p 80, 443 <host>

To perform a TCP null scan to fool a WiFi

>_ nmap -sN <host>