Macro virus

From Saferpedia

A macro virus is a virus written in a macro language, meaning a language built in a software application like a text editor. Because some applications (especially but exclusively parts of Microsoft Office) allow macros it offers a distinct mechanism trough which the virus may spread. This is the reason why it may be dangerous to open unexpected attachments. Modern anitiviruses detects macro viruses.

Foundations

A macro is a set of commands and actions helping tasks automation - a short and simple program. The step that made some applications susceptible to macro viruses was allowing macros to be stored in documents. This makes possible for a document to transport a macro, in a non-obvious way for user.

Operating

A macro may be spread trough e-mail, disks, networks, modems and Internet and it is difficult to detect. Not infected documents contain normal macro. Most infected macro run automatically when the document is opened or closed. A usual method for a macro to infect a computer is to replace normal macros with a virus.

Once the application opens a file containing a macro virus the system may be infected. When is triggered, a macro virus will start to auto-incorporate in other documents and templates and it will do the same with the ones going to be created. The virus will spread to other systems if the infected files are shared with other users.

A very well known example is the Melissa virus from 1999. It was created a document whit a virus incorporated and anyone opening that document infected its system. Afterward the viruses sent itself via e-mail to first 50 persons from user's address book.

Macro viruses can be avoided by being prudent when opening e-mail attachments. Not all macro viruses are detected by antivirus.

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