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AoC3 Day 10: Port Scanning with Nmap

    If you are new to TryHackMe, I recommend checking out their Tutorial room to see how the platform works and how you can access the target machine(s). I also highly recommend using your own “attack box”, be it a Kali, Parrot, or some other pentesting oriented Linux distro (in the form of a VM), as opposed to the browser based solution TryHackMe provides. I’ve found that the browser based VM is a lot slower, though others seem to have no issues with it. The only thing using your own attack VM entails is connecting it to THM’s network through VPN, but this is incredibly easy as TryHackMe will supply you with your own OpenVPN configuration file and is outlined below.

    Types of Challenges

    The TryHackMe platform has multiple types of challenges, each potentially having its own requirements for accessing and completing it. You can identify the type of challenge by looking at the icon on the right-hand side of the collapsible bar for that particular challenge:

    Challenges using the “server rack” icon include the use of a deployable machine, and are the most common. Pressing the “Start Machine” button will launch a virtual machine that you have two ways of accessing: using THM’s “attack box”, found at the top of your browser window:

    Or, you can instead opt to use your own virtual machine connected to the THM network, which is done (on Linux) by clicking your user icon, “Access”, and then “Download My Configuration File”.

    Clicking “Save File”

    And by running the following command in a terminal (I might suggest you move the download to another folder, such as “Documents”):

    Once you see “Initialization Sequence Completed”, you’ll know you’ve successfully connected to THM’s network. Keep this terminal window open (you can minimize it, however). Return to it and press “Ctrl” + “C” twice once you are ready to disconnect.

    After you’ve chosen between THM’s attack box or your own virtual machine, you’ll need the IP address of the target machine, which is what was deployed earlier with the green “Start Machine” button. That information can be seen in a banner at the top of your browser window, or in more detail at the top of the page:

    In many cases you’ll be copying that IP address into your attack box/VM’s browser’s address bar, but in other cases you might be accessing it through SSH, RDP, etc. You’ll notice that you can add time to it if needed, or terminate it if you finish early – opening up more resources for other THM users.

    Challenges using the “browser” icon will require interaction with a simulated website that can be accessed by pressing the “View Site” seen after expanding the challenge. These challenges will need to be completed from within your browser, and cannot be accessed through a VPN on your own machine due to the fact that they are not true websites.

    Challenges with the “download” icon include files – in many cases packet captures (pcaps) or log files to be parsed through using a specific type of software. Where you would like to do this examining is up to you, but you will not be able to use one of TryHackMe’s machines. For examining something like a .pcap file, you will want to install Wireshark on one of your own computers or VMs.

    Challenges without an icon focus on either reading material and answering questions, or will include a link to a publicly accessible website that doesn’t require connection to THM’s network, and therefore can be completed from any computer you choose.

    TryHackMe; Advent of Cyber 3; Day 10

    Day 10 focuses on the use of Nmap to scan hosts on a network and identify their operating systems, open ports, and active services for the purposes of enumeration.

    Start off with a basic TCP connect Nmap scan, which will attempt to initiate a scan on well-known ports 1-1000. The syntax for this command is “nmap -sT <target IP>”. This will tell use how many ports are open in that range, the smallest open port number, and the service related to the highest open port number. We’ll follow up that scan with a TCP SYN scan (-sS) which sends a “RST” (reset) packet upon receiving a SYN/ACK packet, bypassing certain firewall and detection measures. After that, we can gauge whether or not we got the same results.

    Next, we’ll scan the same target with a version scan that will attempt to detect the version of the services that are discovered. We’ll use the “-sV” switch for this. This should reveal the version number of the web server, Apache.

    We can use the link given in the challenge description to visit Apache’s vulnerability changelog for Apache 2.4, finding the CVE number of the vulnerability that 2.4.49 is vulnerable to.

    Now we’ll need to scan even the uncommon ports, which we can do by specifying all ports using the “-p-” switch. We’ll identify a new port number with this method. Make sure to still use the “-sT” switch, as this will make the scan a lot quicker.

    To find the name of the program listening on that port, we’ll want to again employ the “-sV” switch. Rather then running a version scan on all 65,535 ports, we can specify port 20212 specifically using the syntax pictured below.