TryHackMe: Nmap Walkthrough

doretox · March 20, 2021

An in depth look at scanning with nmap, a powerful network scanning tool.

Task 1 - Deploy

No answer needed.

Task 2 - Introduction

  1. What networking constructs are used to direct traffic to the right application on a server?

    Answer: ports

  2. How many of these are available on any network-enabled computer?

    Answer: 65535

  3. [Research] How many of these are considered “well-known”? (These are the “standard” numbers mentioned in the task)

    Answer: 1024

Task 3 - Nmap Switches

  1. What is the first switch listed in the help menu for a ‘Syn Scan’ (more on this later!)?

    Answer: -sS

  2. Which switch would you use for a “UDP scan”?

    Answer: -sU

  3. If you wanted to detect which operating system the target is running on, which switch would you use?

    Answer: -O

  4. Nmap provides a switch to detect the version of the services running on the target. What is this switch?

    Answer: -sV

  5. The default output provided by nmap often does not provide enough information for a pentester. How would you increase the verbosity?

    Answer: -v

  6. Verbosity level one is good, but verbosity level two is better! How would you set the verbosity level to two?

    Answer: -vv

  7. What switch would you use to save the nmap results in three major formats?

    Answer: -oA

  8. What switch would you use to save the nmap results in a “normal” format?

    Answer: -oN

  9. A very useful output format: how would you save results in a “grepable” format?

    Answer: -oG

  10. Sometimes the results we’re getting just aren’t enough. If we don’t care about how loud we are, we can enable “aggressive” mode. This is a shorthand switch that activates service detection, operating system detection, a traceroute and common script scanning.

    How would you activate this setting?

Answer: -A

  1. Nmap offers five levels of “timing” template. These are essentially used to increase the speed your scan runs at. Be careful though: higher speeds are noisier, and can incur errors!

    How would you set the timing template to level 5?

    Answer: -T5

  2. We can also choose which port(s) to scan.

    How would you tell nmap to only scan port 80?

    Answer: -p 80

  3. How would you tell nmap to scan ports 1000-1500?

    Answer: -p 1000-1500

  4. A very useful option that should not be ignored:

    How would you tell nmap to scan all ports?

    Answer: -p-

  5. How would you activate a script from the nmap scripting library (lots more on this later!)?

    Answer: –script

  6. How would you activate all of the scripts in the “vuln” category?

    Answer: –script=vuln

Task 4 - [Scan Types] Overview

No answer needed.

Task 5 - [Scan Types]

  1. hich RFC defines the appropriate behaviour for the TCP protocol?

    Answer: RFC 793

  2. If a port is closed, which flag should the server send back to indicate this?

    Answer: RST

Task 6 - [Scan Types] SYN Scans

  1. There are two other names for a SYN scan, what are they?

    Answer: Half-Open, Stealth

  2. Can Nmap use a SYN scan without Sudo permissions (Y/N)?

    Answer: N

Task 7 - [Scan Types] UDP Scans

  1. If a UDP port doesn’t respond to an Nmap scan, what will it be marked as?

    Answer: Nmap open-filtered

  2. When a UDP port is closed, by convention the target should send back a “port unreachable” message. Which protocol would it use to do so?

    Answer: ICMP

Task 8 - [Scan Types] NULL, FIN and Xmas

  1. Which of the three shown scan types uses the URG flag?

Answer: xmas

  1. Why are NULL, FIN and Xmas scans generally used?

Answer: Firewall Evasion

  1. Which common OS may respond to a NULL, FIN or Xmas scan with a RST for every port?

Answer: Microsoft Windows

# Task 9 - [Scan Types] ICMP Network Scanning

  1. How would you perform a ping sweep on the 172.16.x.x network (Netmask: 255.255.0.0) using Nmap? (CIDR notation)

Answer: nmap -sn 172.16.0.0/16

Task 10 - [NSE Scripts] Overview

  1. What language are NSE scripts written in?

Answer: Lua

  1. Which category of scripts would be a very bad idea to run in a production environment?

Answer: intrusive

Task 11 - [NSE Scripts] Working with the NSE

  1. What optional argument can the ftp-anon.nse script take?

    Answer: maxlist

Task 12 - [NSE Scripts] Searching for Scripts

  1. Search for “smb” scripts in the /usr/share/nmap/scripts/directory using either of the demonstrated methods. What is the filename of the script which determines the underlying OS of the SMB server?

    Answer: smb-os-discovery.nse

  2. Read through this script. What does it depend on?

    Answer: smb-brute

Task 13 - Firewall Evasion

  1. Which simple (and frequently relied upon) protocol is often blocked, requiring the use of the -Pn switch?

    Answer: ICMP

  2. [Research] Which Nmap switch allows you to append an arbitrary length of random data to the end of packets?

    Answer: –data-lenght

Task 14 - Practical

  1. Does the target (MACHINE_IP) respond to ICMP (ping) requests (Y/N)?

    Nmap Ping

    Answer: N

  2. Perform an Xmas scan on the first 999 ports of the target – how many ports are shown to be open or filtered?

    Nmap Xmass

    Answer: 999

  3. There is a reason given for this – what is it?

    Nmap No Response

    Answer: no response

  4. Perform a TCP SYN scan on the first 5000 ports of the target – how many ports are shown to be open?

    Nmap TCP SYN Scan

    Answer: 5

  5. Deploy the ftp-anon script against the box. Can Nmap login successfully to the FTP server on port 21? (Y/N)

    Nmap ftp-anon script

    Answer: Y

Task 15 - Conclusion

No answer needed.

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