How to Install & use the NMAP Security Scanner on Linux

NMAP.sh

#!/bin/sh

sudo apt-get update
sudo apt-get install nmap
nmap --version

#Scan IP range or subnet
sudo nmap target_IP or domain.com

#Port Specification and Scan Order
sudo nmap –p 80,443 185.34.65.632
sudo nmap –sU –p 80,130,255 185.34.65.632

#TCP SYN scan
sudo nmap -sS 185.34.65.632

#TCP scan
sudo nmap –sT 185.34.65.632

#Nmap: Scan Speed, Aggression, and Verbosity
sudo nmap –A –T4 –v –Pn reddit.com

#NB: Aggressive Scan-: -A, Scan Output-: –v, Scan Speed-: -T0 (T0 and span to T5)

#Scan port 80 on the target system:
nmap –p 80 185.34.65.632

#Scan ports 1 through 200 on the target system:
nmap –p 1-200 185.34.65.632

#Scan (Fast) the most common ports:
nmap –F 185.34.65.632

#To scan all ports (1 – 65535):
nmap –p– 185.34.65.632

#Here is a brief list of standard ports and their designations:

21 – FTP
22 – SSH
25 – SMTP (sending email)
53 – DNS (domain name service)
80 – HTTP (web server)
110 – POP3 (email inbox)
123 – NTP (Network Time Protocol)
143 – IMAP (email inbox)
443 – HTTPS (secure web server)
465 – SMTPS (send secure email)
631 – CUPS (print server)
993 – IMAPS (secure email inbox)
995 – POP3 (secure email inbox)
#A Linux firewall can be configured to block all traffic on a particular port.