computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes, and development of both hardware and software. Computing has scientific, ...

terminology, a macro virus is a

virus A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsk ...

that is written in a macro

language Language is a structured system of communication. The structure of a language is its grammar and the free components are its vocabulary. Languages are the primary means by which humans communicate, and may be conveyed through a variety of ...

: a programming language which is embedded inside a software application (e.g., word processors and spreadsheet applications). Some applications, such as

Microsoft Office Microsoft Office, or simply Office, is the former name of a family of client software, server software, and services developed by Microsoft. It was first announced by Bill Gates on August 1, 1988, at COMDEX in Las Vegas. Initially a marketi ...

Excel ExCeL London (an abbreviation for Exhibition Centre London) is an exhibition centre, international convention centre and former hospital in the Custom House area of Newham, East London. It is situated on a site on the northern quay of the ...

PowerPoint Microsoft PowerPoint is a presentation program, created by Robert Gaskins and Dennis Austin at a software company named Forethought, Inc. It was released on April 20, 1987, initially for Macintosh computers only. Microsoft acquired PowerPo ...

allow macro programs to be embedded in documents such that the macros are run automatically when the document is opened, and this provides a distinct mechanism by which malicious computer instructions can spread. This is one reason it can be dangerous to open unexpected attachments in

e-mail Electronic mail (email or e-mail) is a method of exchanging messages ("mail") between people using electronic devices. Email was thus conceived as the electronic (digital) version of, or counterpart to, mail, at a time when "mail" meant ...

s. Many antivirus programs can detect macro viruses; however, the macro virus' behavior can still be difficult to detect .

Fundamentals

A macro is a series of commands and actions that helps automating some tasks - usually a quite short and simple program. However they are created, they need to be executed by some system which interprets the stored commands. Some macro systems are self-contained programs, but others are built into complex applications (for example word processors) to allow users to repeat sequences of commands easily, or to allow developers to tailor the application to local needs.

Operation

A macro virus can be spread through e-mail attachments, removable media,

networks Network, networking and networked may refer to: Science and technology * Network theory, the study of graphs as a representation of relations between discrete objects * Network science, an academic field that studies complex networks Mathematics ...

and the

Internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, pub ...

, and is notoriously difficult to detect. A common way for a macro virus to infect a computer is by replacing normal macros with a virus. The macro virus replaces regular commands with the same name and runs when the command is selected. These malicious macros may start automatically when a document is opened or closed, without the user's knowledge. Once a file containing a macro virus is opened, the virus can infect the system. When triggered, it will begin to embed itself in other documents and templates. It may corrupt other parts of the system, depending on what resources a macro in this application can access. When the infected documents are shared with other users and systems, the virus spreads. Macro viruses have been used as a method of installing software on a system without the user's consent, as they can be used to download and install software from the internet through the use of automated key-presses. However, this is uncommon as it is usually not fruitful for the virus coder since the installed software is usually noticed and uninstalled by the user. Since a macro virus depends on the application rather than the

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also i ...

, it can infect a computer running any operating system to which the targeted application has been ported. In particular, since Microsoft Word is available on

Macintosh The Mac (known as Macintosh until 1999) is a family of personal computers designed and marketed by Apple Inc. Macs are known for their ease of use and minimalist designs, and are popular among students, creative professionals, and software en ...

computers, word macro viruses can attack some Macs in addition to Windows platforms. An example of a macro virus is the Melissa virus which appeared in March 1999. When a user opens a Microsoft Word document containing the Melissa virus, their computer becomes infected. The virus then sends itself by email to the first 50 people in the person's address book. This made the virus replicate at a fast rate. Not all macro viruses are detected by

antivirus software Antivirus software (abbreviated to AV software), also known as anti-malware, is a computer program used to prevent, detect, and remove malware. Antivirus software was originally developed to detect and remove computer viruses, hence the name. ...

. Caution when opening email attachments and other documents decreases the chance of becoming infected. Due to the prevalence of macro viruses, starting with

Microsoft Office 2007 Microsoft Office 2007 (codenamed Office 12) is an office suite for Windows, developed and published by Microsoft. It was officially revealed on March 9, 2006 and was the 12th version of Microsoft Office. It was released to manufacturing on Novem ...

, Microsoft assigned a separate set of

file extension A filename extension, file name extension or file extension is a suffix to the name of a computer file (e.g., .txt, .docx, .md). The extension indicates a characteristic of the file contents or its intended use. A filename extension is typically d ...

s ending in "m" to Office files containing macros in order to prevent users from opening macro virus-infected files that were not intended to contain macros in the first place. On the 9th of February,

Microsoft Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washin ...

announced that Office files originating from the internet will have their macros blocked by default, starting from April of 2022.

Fundamentals

Operation

See also

References

Further reading