A virus written into a macro (script) in a Microsoft Word document or template. With hundreds of kinds discovered over the years, the macro virus executes and does its damage when the Word document is opened. The macro virus may also attach itself to the Normal Word template so that new documents are created with the corruption. To prevent a virus from executing, a dubious Word document can always be opened with macros turned off. See
Word macro,
Melissa virus and
letter bomb.