Macro viruses

Written by a NortonLifeLock employee


A macro virus is defined as “a computer virus written in the same macro language used for software applications, such as word processors.” Microsoft Word and Excel are two examples of applications that feature powerful macro languages, which are embedded in documents so they run automatically when the documents are open. A macro virus subsequently releases a “chain of events in conjunction with the application.”

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How They Spread

Macro viruses spread whenever a user opens or closes an infected document. The most common methods of spreading such viruses include:

  • Email attachments
  • CD-ROM
  • Internet

As with many other forms of viruses and malware, macro viruses are difficult to detect.

What They Do

These viruses are programmed to do practically anything with a PC. This means a macro virus is capable of creating new files, corrupting data, moving text, sending files, formatting hard drives, and inserting pictures among other things. One of their more popular uses is as transportation for destructive viruses and malware.

A Classic Example

A now-classic example of a macro virus is the Melissa Virus from 1999. Opening an email containing a document infected with the virus would cause the email to send itself to the first 50 addresses in the user’s contact list. The virus subsequently replicated at an extraordinarily fast rate.

Application Rather Than Operating System

Because a macro virus centers on an application rather than an operating system, it has the ability to infect any operating system, including those on non-Windows computers.

Symptoms of a Macro Virus Infection

Symptoms of a macro virus infection include:

  • Your computer runs slower than normal.
  • Your computer asks you for a password on a file that normally doesn’t require one.
  • Your computer saves documents as “template” files.
  • Your computer features strange error messages.

How Do I Get Rid of a Macro Virus?

Getting rid of a macro virus requires taking it to a professional or checking manually for virus signs.

“To check for viruses manually, choose Tools | Macro | Macros and compare the resulting list of macros with the list you created earlier,” M. David Stone wrote for PC Mag in 2001. “Follow this procedure with the Macros in: box set for and for each file in your Startup folder.

“Pay particularly close attention to any macros named AutoExec, AutoOpen, AutoClose, FileExit, FileNew, FileOpen, FileSave, FileSaveAs, and ToolsMacro,” Stone added. “The first three names identify macros that run automatically. The rest replace built-in commands in Word and are common choices for viruses. If you have legitimate macros with these names, look at the contents of each with the aid of the Edit button. If none of your macros have been replaced or modified by a virus, you're almost certainly virus-free.

”How Do I Prevent Macro Viruses From Infecting My Computer?

As with all forms of cyber viruses and malware, prevention is best. Use the following tips to protect your computer:

  • Update your security system regularly to guard against new types of viruses.
  • Update your computer regularly to ensure optimal protection. For example, if you have Windows 8 and are being prompted to update to Windows 10, do it.
  • Use digital signatures. They identify download sources so you can be sure what you’re downloading and running isn’t a risk.
  • Download reputable antivirus software if you haven’t already.

Macro viruses are among the sneakier methods of infecting a computer. Stay aware of the latest information on these and all other cyber viruses, and give your computer a thorough scan if it hasn’t had one in awhile. And again, if you’ve been ignoring update notifications, now is the time to take action.

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Disclaimers and references:
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