nmap scan tool

Last updated: Mar 20, 2024

Main Options

sT : TCP connect scan, better use SYN which is quicker and stealthy.
sS : TCP SYN scan, also known as half-open scanning, quite unobtrusive and stealthy, since it never completes TCP connections.
sU : UDP scan
sP : PING scanning for host discovery, a ICMP echo request is sent.
PR : ARP scan.
F : Fast scan, only scan ports included inside nmap-services file.
p1-65535 : port interval, here we scan every ports.
PN : force scan, even if no ping response from adresses.
P0 : Same as PN.
O : Try to determine OS target.
oG : save result into file.
n : disable DNS resolution.
R : enable DNS resolution.
iR : random target scan.

Examples

TCP connect, scan ports from 1 to 65535, force scan, try to guess OS, target is 192.168.1.1. Save results inside /tmp/001 file.

root@host:~# nmap -sT -p1-65535 -P0 -O -oG /tmp/001 192.168.1.1

Scan 192.168.1.0/24 hosts family addresses:

root@host:~# nmap 192.168.1.0-255

Scan SYN, random hosts, web service:

root@host:~# nmap -sS -iR 0 -p 80

Spoof source address (10.0.0.0). Scan 10.0.0.1 host, set source port to 80:

root@host:~# nmap -S 10.0.0.0 -g 80 10.0.0.1

Host Discovery scan for 10.0.0.0/24 network. Result will show ip and MAC addresses:

root@host:~# nmap -sP 10.0.0.0/24

Complete scan of the scanme.nmap.org host. TCP SYN scan on every ports -p-, we consider the host as active -PN, agressive scan (-A include services version detection -sV, Script Engine -sC, OS detection -O and --traceroute).

root@host:~# nmap -sS -PN -p- -A -T4 scanme.nmap.org

SSH Algorithms Scan

Show algorithms that the target SSH2 server offers, it's useful when encountering the message: "Unable to negotiate with 192.168.1.1 port 22: no matching host key type found. Their offer: ssh-rsa,ssh-dss":

root@host:~# nmap -p 22 --script ssh2-enum-algos 192.168.1.1
Starting Nmap 7.93 ( https://nmap.org ) at 2023-12-08 19:26 CET
Nmap scan report for 192.168.1.1
Host is up (0.0056s latency).

PORT   STATE SERVICE
22/tcp open  ssh
| ssh2-enum-algos: 
|   kex_algorithms: (3)
|       diffie-hellman-group16-sha512
|       diffie-hellman-group14-sha1
|       diffie-hellman-group1-sha1
|   server_host_key_algorithms: (2)
|       ssh-rsa
|       ssh-dss
|   encryption_algorithms: (4)
|       aes128-ctr
|       aes192-ctr
|       aes256-ctr
|       chacha20-poly1305@openssh.com
|   mac_algorithms: (3)
|       hmac-sha2-256
|       hmac-sha2-512
|       hmac-sha1
|   compression_algorithms: (1)
|_      none

Nmap done: 1 IP address (1 host up) scanned in 0.60 seconds

Based on the reported information, we can deduce the SSH algorithms to configure:

root@host:~# ssh -o KexAlgorithms=+diffie-hellman-group16-sha512 -o HostKeyAlgorithms=+ssh-rsa 192.168.1.1

sources : tux-planet, nmap.org

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Misc

nmap scan tool

Main Options

Examples

SSH Algorithms Scan