I will therefore break the topic down into a few selected topics. The Computer Virus Structure Troy Kammerdiener from Keene University wrote an excellent presentation on the topic of computer viruses. In one section of the presentation he discusses the structure of a computer virus. According to the Dental School at the University of Washington, a macro virus is a virus that attaches itself to a document. Now that application programs like MS Word and MS Excel are utilizing very powerful 'macro languages' to better suit the needs of us, the consumer, it has also opened the door to a brand new, highly effective way of creating viruses.
Macro viruses are very easy to create or modify.
The distinguishing factor that makes it possible to create a virus with a macro is the existence of auto-execute macros in the macro language. An auto-execute macro is one that is executed in response to an event such as opening or closing a file and not in response to an explicit user command. Once a Macro virus is running, it can copy itself to other documents, delete files, and create general problems in a system. These things occur without the user explicitly running the macro. Macro viruses spread by having one or more auto-execute macros in a document.