Last Updated on January 25, 2022 by aghanim

This is my notes from the Junior Pentesting course at TryHackMe. This course takes you through the basics and some advanced topics regarding penetration testing.

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NMAP Live Host Discovery

Scan Type	Example Command
ARP Scan	sudo nmap -PR -sn MACHINE_IP/24
ICMP Echo Scan	sudo nmap -PE -sn MACHINE_IP/24
ICMP Timestamp Scan	sudo nmap -PP -sn MACHINE_IP/24
ICMP Address Mask Scan	sudo nmap -PM -sn MACHINE_IP/24
TCP SYN Ping Scan	sudo nmap -PS22,80,443 -sn MACHINE_IP/30
TCP ACK Ping Scan	sudo nmap -PA22,80,443 -sn MACHINE_IP/30
UDP Ping Scan	sudo nmap -PU53,161,162 -sn MACHINE_IP/30

Remember to add -sn if you are only interested in host discovery without port-scanning. Omitting -sn will let Nmap default to port-scanning the live hosts.

Option	Purpose
-n	no DNS lookup
-R	reverse-DNS lookup for all hosts
-sn	host discovery only

NMAP Basic Port Scans

1. Open: indicates that a service is listening on the specified port.
2. Closed: indicates that no service is listening on the specified port, although the port is accessible. By accessible, we mean that it is reachable and is not blocked by a firewall or other security appliances/programs.
3. Filtered: means that Nmap cannot determine if the port is open or closed because the port is not accessible. This state is usually due to a firewall preventing Nmap from reaching that port. Nmap’s packets may be blocked from reaching the port; alternatively, the responses are blocked from reaching Nmap’s host.
4. Unfiltered: means that Nmap cannot determine if the port is open or closed, although the port is accessible. This state is encountered when using an ACK scan -sA.
5. Open|Filtered: This means that Nmap cannot determine whether the port is open or filtered.
6. Closed|Filtered: This means that Nmap cannot decide whether a port is closed or filtered.

TCP Flags

1. URG: Urgent flag indicates that the urgent pointer filed is significant. The urgent pointer indicates that the incoming data is urgent, and that a TCP segment with the URG flag set is processed immediately without consideration of having to wait on previously sent TCP segments.
2. ACK: Acknowledgement flag indicates that the acknowledgement number is significant. It is used to acknowledge the receipt of a TCP segment.
3. PSH: Push flag asking TCP to pass the data to the application promptly.
4. RST: Reset flag is used to reset the connection. Another device, such as a firewall, might send it to tear a TCP connection. This flag is also used when data is sent to a host and there is no service on the receiving end to answer.
5. SYN: Synchronize flag is used to initiate a TCP 3-way handshake and synchronize sequence numbers with the other host. The sequence number should be set randomly during TCP connection establishment.
6. FIN: The sender has no more data to send.

Timings

Timings	Description
T0	paranoid (0)
T1	sneaky (1)
T2	polite (2)
T3	normal (3)
T4	aggressive (4)
T5	insane (5)

Summary

Port Scan Type	Example Command
TCP Connect Scan	nmap -sT MACHINE_IP
TCP SYN Scan	sudo nmap -sS MACHINE_IP
UDP Scan	sudo nmap -sU MACHINE_IP

These scan types should get you started discovering running TCP and UDP services on a target host.

Option	Purpose
-p-	all ports
-p1-1023	scan ports 1 to 1023
-F	100 most common ports
-r	scan ports in consecutive order
-T<0-5>	-T0 being the slowest and T5 the fastest
–max-rate 50	rate <= 50 packets/sec
–min-rate 15	rate >= 15 packets/sec
–min-parallelism 100	at least 100 probes in parallel

NMAP Advanced Port Scans

Port Scan Type	Example Command
TCP Null Scan	sudo nmap -sN MACHINE_IP
TCP FIN Scan	sudo nmap -sF MACHINE_IP
TCP Xmas Scan	sudo nmap -sX MACHINE_IP
TCP Maimon Scan	sudo nmap -sM MACHINE_IP
TCP ACK Scan	sudo nmap -sA MACHINE_IP
TCP Window Scan	sudo nmap -sW MACHINE_IP
Custom TCP Scan	sudo nmap --scanflags URGACKPSHRSTSYNFIN MACHINE_IP
Spoofed Source IP	sudo nmap -S SPOOFED_IP MACHINE_IP
Spoofed MAC Address	--spoof-mac SPOOFED_MAC
Decoy Scan	nmap -D DECOY_IP,ME MACHINE_IP
Idle (Zombie) Scan	sudo nmap -sI ZOMBIE_IP MACHINE_IP
Fragment IP data into 8 bytes	-f
Fragment IP data into 16 bytes	-ff

Option	Purpose
--source-port PORT_NUM	specify source port number
--data-length NUM	append random data to reach given length

These scan types rely on setting TCP flags in unexpected ways to prompt ports for a reply. Null, FIN, and Xmas scan provoke a response from closed ports, while Maimon, ACK, and Window scans provoke a response from open and closed ports.

Option	Purpose
–reason	explains how Nmap made its conclusion
-v	verbose
-vv	very verbose
-d	debugging
-dd	more details for debugging

NMAP Post Port Scans

Option	Meaning
-sV	determine service/version info on open ports
-sV –version-light	try the most likely probes (2)
-sV –version-all	try all available probes (9)
-O	detect OS
–traceroute	run traceroute to target
–script=SCRIPTS	Nmap scripts to run
-sC or –script=default	run default scripts
-A	equivalent to -sV -O -sC --traceroute
-oN	save output in normal format
-oG	save output in grepable format
-oX	save output in XML format
-oA	save output in normal, XML and Grepable formats