Macro Virus: What It is, How It Works, Prevention

What Is a Macro Virus?

A macro virus infects a software program and causes actions to begin automatically when the program is opened. It operates like a normal macro and often installs itself in place of an existing macro.

Key Takeaways

• A macro virus is a type of computer exploit or malware that triggers software functions, often with deleterious effect.
• In addition to wreaking havoc on a system, macro viruses also program to replicate and spread themselves to infect other systems.
• Macro viruses spread online via phony web links or as e-mail attachments.
• Antivirus software is good at detecting and removing macro viruses before harm is done.

Understanding Macro Viruses

Macro viruses originate on the internet and infiltrate programs installed on a person’s computer. To understand what a macro virus is, it is important to first know what a "macro" is:

A macro is a series of commands that triggers a specific function within a software program. Macros can be installed in programs such as Microsoft Word to perform complex tasks that the program cannot do automatically. For example, a company can use a macro to insert designed letterhead or pre-designed tables into Microsoft Word page templates or use custom page formats not available with the program itself.

Macro viruses are encoded to spread, much like a virus infects a person, replicates, and spreads to others. A macro virus can replicate and install material on a computer without the user’s knowledge or consent. If sent through email spam, it often automatically sends itself to everyone in the user’s address book.

How Does a Macro Virus Infect a Computer?

Macro viruses originate on the Internet, often in spam email, and infiltrate programs installed on a person’s computer, such as Microsoft Office, by imitating a benign macro. They take the place of pre-installed macros and are activated when the regular macro is executed, but they can operate even when the program is not in use without the user’s knowledge. The actions they trigger can range from adding text uncontrollably to a document to sending spam messages to the user’s address books.

Macro viruses are often harmless to the computer or the program itself, but they cause confusion and frustration for the user. Once installed, they can spread across multiple programs if not contained.

How to Prevent Macro Viruses

Most antivirus software today are designed to find and destroy existing macro viruses on a computer and prevent new ones from taking root. However, not all macro viruses are detected by antivirus software, and not all antivirus software are alike. Maintain up-to-date antivirus software and be conscious of what you download or open from the Internet.

For example, do not open an attachment in an email from an unknown address. Email spam can be easily identifiable, but it can also use tricks to make content appear legitimate.