Macro Virus: Definition, Operation, Prevention & Removal

A macro virus is a malicious program written in the same code as the software program it targets for system entry.

Software programs, such as Microsoft Word, rely on a web of code that sits just beneath the surface. Micro viruses are written in the same language, and your computer can't tell the difference between valid and malignant code.

If you're infected with a macro virus, your software can behave in unexpected ways. And you could infect plenty of other people and never know it.

What Is a Macro Virus?

A macro virus is a malicious piece of code embedded within software. During an attack, your program doesn't respond in an expected manner. And you may send many copies to others during your workday. 

Coding starts the process. A hacker writes something that sits deep inside common software, such as those in the Microsoft suite. The macro may look like it does something harmless (like help you to save a file), but it can do something else either instead or at the same time. 

If you're infected with a macro virus, you might experience:

  • Strange demands. You might get asked to enter passwords when opening or saving files, even if you never needed them before. 
  • Unusual formats. Your documents might get saved as templates rather than standard files.
  • Cries of alarm. You might get notes from colleagues about files you don't remember sending. 

A macro virus is meant to remain hidden. You won't see an alert in your files as you work on them. But the code deploys each time you meet the hacker's specific demands.

How Do Macro Viruses Work?

Hackers manipulate macros, and they're available in almost every type of software. Macros make all of the small, repetitive tasks we complete bearable. 

For example, when we open a new document in Word, we use a Normal template based on a Normal macro. Your new document comes preloaded with the fonts you like, the paper size you use, and more. 

Hackers love to manipulate the normal macro, experts say, as users may lean on it dozens of times each day. But you might also have macros that help you:

  • Load Word. 
  • Open an existing document.
  • Create a new document. 
  • Close a document. 
  • Quit Word. 

Any of these could be touched or tampered with by a malicious macro. Or the hacker could create a new macro from scratch to infect your files.

When your computer is infected, you tend to spread it to others. All the files on your server might be affected by it, and each time a coworker opens a file, it deploys again. 

It's easy to complain about people who open infected files and download virus content. But new macro viruses come with clever prompts that push users to take action. You might see a warning that says you need to hit "Enable Features" to read the content, for example. Doing so can load the virus. 

If your system isn't yet infected with a macro virus, it could get it from outside. You might get an email with a tainted attachment, for example, or you might get a memory stick loaded with infection.

How Can a Macro Virus Hurt You?

Some macro viruses just seem irritating. You want to do your work, but your software isn't following the commands you tap out. But some forms of macro virus can be incredibly damaging. 

Some known macro viruses can:

  • Delete. They might wipe out files altogether, or they might remove every other word. 
  • Add. They might put political statements into all of your files, or they might place garbled language between your paragraphs. 
  • Move. They might shift the placement of your text or change where your files are saved. 
  • Corrupt. Some macro viruses can take down your hard drive. 
  • Overload. A macro might send tainted email messages to everyone in your contact list, and your server may not be able to handle the traffic. 

In 1999, a large micro virus known as Melissa spread across the internet, and it eventually took down email servers at more than 300 corporations. The FBI says cleanup cost an estimated $80 million. Stories like this prove that macro viruses just can’t be ignored.

How to Remove a Macro Virus 

To keep a macro virus from spreading, all infected files must be deleted as quickly as possible. Take out the files, and you could protect all of your colleagues and your system as a whole. 

Microsoft says spotting the files isn't always easy. If you know where macros are stored in your system, scan through the folder and delete anything that seems unusual or out of the ordinary. 

If you can't find the files or you're not sure where the problem starts:

  • Reboot the infected computers in Safe Mode. 
  • Delete all temporary files. 
  • Perform a virus scan. 

Look for continued problems, including poor or unexplained performance. If the issues persist, try a different virus scan tool.

How to Prevent a Macro Virus Infection

No one wants to deal with cleanup. Tossing infected files can mean losing hours or even days of work. Preventing the problem is a wiser choice. 

Your prevention plan should include:

  • Antivirus scans. Use software to examine all the files on your computer or server. If you're about to download a file and get an alert about infection, stop and listen. Never override the rules. 
  • Software updates. When the manufacturers send patches to repair known vulnerabilities, download and apply them immediately. 
  • Suspicion. Don't click on or open files from people you don't know. And if unusual messages with attachments come from coworkers, flag them for IT. 

In the early 2000s, most people responded to files from outsiders with suspicion. But as experts point out, many of us haven't seen a macro virus in years. We've let down our collective guard, even though the risks persist. Be cautious about any kind of software to keep your company safe.

Protection From Okta 

We've developed plenty of programs to help protect your company from macro viruses. For example, we can help you build and implement a firewall to keep malicious email from reaching your employees. And our scanners can help you spot an attack in progress.

Contact us to find out more.


Macro Viruses. The University of Maryland. 

Macro Malware on the Rise Again. (November 2014). Virus Bulletin. 

What Is a Macro Virus and How Do I Remove It? (November 2020). Cybernews. 

The Melissa Virus. (March 2019). U.S. Department of Justice. 

Frequently Asked Questions About Word Macro Viruses. (April 2018). Microsoft. 

The Rise, Fall, and Rise of the Macro Virus. (October 2014). IDG Connect.