Macro virus (computing)
Encyclopedia
In computing
terminology, a macro virus is a virus
that is written in a macro language
: that is to say, a language built into a software application such as a word processor. Since some applications (notably, but not exclusively, the parts of Microsoft Office
) allow macro programs to be embedded in documents, so that the programs may be run automatically when the document is opened, this provides a distinct mechanism by which viruses can be spread. This is why it may be dangerous to open unexpected attachments
in e-mail
s. Modern antivirus software
detects macro viruses as well as other types.
, but usually quite short and simple. 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.
The step which has made some applications susceptible to macro viruses was to allow macros to be stored in the very documents which are being edited or processed by the application. This makes it possible for a document to carry a macro, not obvious to the user, which will be executed automatically on opening the document.
s, disc
s, networks
, modem
s, and the Internet
and is notoriously difficult to detect. Uninfected documents contain normal macros. Most malicious macros start automatically when a document is opened or closed. A common way for a macro virus to infect a computer is by replacing normal macros with the virus. The macro virus replaces the regular commands with the same name and runs when the command is selected. In the cases where the macro is run automatically, the macro is opened without the user knowing.
Once the application opens a file that contains a macro virus, the virus can infect the system. When triggered, it will begin to embed itself in other documents and templates, as well as future ones created. It may corrupt other parts of the system as well, depending on what resources a macro in this application can get access to. As the infected documents are shared with other users and systems, the virus will spread. The macro virus has also been known to be used as a way of installing software on a system without the users consent as it can be used to look up software and web pages on the internet, go through with downloading and installing the software through the use of automated key-presses etc, however this is uncommon as it is usually un-fruitful for the virus coder since the installed software is usually noticed and uninstalled by the user.
A well known example of a macro virus is the Melissa Virus
from 1999. Anyone who opened a document with the virus in Microsoft Office would 'catch' the virus. The virus would then send itself by email to the first 50 people in the person’s address book. This made the virus replicate at a fast rate.
Since a macro virus depends on the application rather than the operating system
, 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
computers, word macro viruses can attack these as well as Windows platforms.
The macro virus can be avoided by exercising caution when opening email attachments and other documents. Not all macro viruses can be detected by antivirus software
.
Computing
Computing is usually defined as the activity of using and improving computer hardware and software. It is the computer-specific part of information technology...
terminology, a macro virus is a virus
Computer virus
A computer virus is a computer program that can replicate itself and spread from one computer to another. The term "virus" is also commonly but erroneously used to refer to other types of malware, including but not limited to adware and spyware programs that do not have the reproductive ability...
that is written in a macro language
Programming language
A programming language is an artificial language designed to communicate instructions to a machine, particularly a computer. Programming languages can be used to create programs that control the behavior of a machine and/or to express algorithms precisely....
: that is to say, a language built into a software application such as a word processor. Since some applications (notably, but not exclusively, the parts of Microsoft Office
Microsoft Office
Microsoft Office is a non-free commercial office suite of inter-related desktop applications, servers and services for the Microsoft Windows and Mac OS X operating systems, introduced by Microsoft in August 1, 1989. Initially a marketing term for a bundled set of applications, the first version of...
) allow macro programs to be embedded in documents, so that the programs may be run automatically when the document is opened, this provides a distinct mechanism by which viruses can be spread. This is why it may be dangerous to open unexpected attachments
E-mail attachment
An email attachment is a computer file sent along with an email message. One or more files can be attached to any email message, and be sent along with it to the recipient. This is typically used as a simple method to share documents and images...
in e-mail
E-mail
Electronic mail, commonly known as email or e-mail, is a method of exchanging digital messages from an author to one or more recipients. Modern email operates across the Internet or other computer networks. Some early email systems required that the author and the recipient both be online at the...
s. Modern antivirus software
Antivirus software
Antivirus or anti-virus software is used to prevent, detect, and remove malware, including but not limited to computer viruses, computer worm, trojan horses, spyware and adware...
detects macro viruses as well as other types.
Fundamentals
A macro is a series of commands and actions that help to automate some tasks - effectively a programComputer program
A computer program is a sequence of instructions written to perform a specified task with a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute...
, but usually quite short and simple. 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.
The step which has made some applications susceptible to macro viruses was to allow macros to be stored in the very documents which are being edited or processed by the application. This makes it possible for a document to carry a macro, not obvious to the user, which will be executed automatically on opening the document.
Operation
A macro virus can be spread through e-mail attachmentE-mail attachment
An email attachment is a computer file sent along with an email message. One or more files can be attached to any email message, and be sent along with it to the recipient. This is typically used as a simple method to share documents and images...
s, disc
Disk storage
Disk storage or disc storage is a general category of storage mechanisms, in which data are digitally recorded by various electronic, magnetic, optical, or mechanical methods on a surface layer deposited of one or more planar, round and rotating disks...
s, networks
Computer network
A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....
, modem
Modem
A modem is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data...
s, and the Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
and is notoriously difficult to detect. Uninfected documents contain normal macros. Most malicious macros start automatically when a document is opened or closed. A common way for a macro virus to infect a computer is by replacing normal macros with the virus. The macro virus replaces the regular commands with the same name and runs when the command is selected. In the cases where the macro is run automatically, the macro is opened without the user knowing.
Once the application opens a file that contains a macro virus, the virus can infect the system. When triggered, it will begin to embed itself in other documents and templates, as well as future ones created. It may corrupt other parts of the system as well, depending on what resources a macro in this application can get access to. As the infected documents are shared with other users and systems, the virus will spread. The macro virus has also been known to be used as a way of installing software on a system without the users consent as it can be used to look up software and web pages on the internet, go through with downloading and installing the software through the use of automated key-presses etc, however this is uncommon as it is usually un-fruitful for the virus coder since the installed software is usually noticed and uninstalled by the user.
A well known example of a macro virus is the Melissa Virus
Melissa (computer worm)
The Melissa virus, also known as "Mailissa", "Simpsons", "Kwyjibo", or "Kwejeebo", is a mass-mailing macro virus. As it is not a standalone program, it is not a worm.-History:...
from 1999. Anyone who opened a document with the virus in Microsoft Office would 'catch' the virus. The virus would then send itself by email to the first 50 people in the person’s address book. This made the virus replicate at a fast rate.
Since a macro virus depends on the application rather than the operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
, 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
Macintosh
The Macintosh , or Mac, is a series of several lines of personal computers designed, developed, and marketed by Apple Inc. The first Macintosh was introduced by Apple's then-chairman Steve Jobs on January 24, 1984; it was the first commercially successful personal computer to feature a mouse and a...
computers, word macro viruses can attack these as well as Windows platforms.
The macro virus can be avoided by exercising caution when opening email attachments and other documents. Not all macro viruses can be detected by antivirus software
Antivirus software
Antivirus or anti-virus software is used to prevent, detect, and remove malware, including but not limited to computer viruses, computer worm, trojan horses, spyware and adware...
.
Common macro viruses
- Concept virusConcept virusThe name Concept virus refers to two different pieces of computer malware, each of which has acted as a proof of concept for a new method of propagation:...
- Melissa (Computer Virus)
- wm/cap
- Papab
Further reading
- Microsoft Corporation. (2006). Introduction to Security. Retrieved June 18, 2006
- The Trustees of Indiana University. (2006). What are computer Viruses, Worms, and Trojan Horses? Retrieved June 18, 2006
- Macro Viruses from Security News & Information