From a security standpoint, the Internet represents a double threat. First, the Internet has introduced new ways of writing viruses and other malicious programs using technologies such as ActiveX controls and Java applets. Second, the Internet makes it vastly easier for viruses to spread via e-mail and downloads. These methods of transferring viruses have played a big role in the sudden rise of macro viruses. Macro viruses spread via infected files, such as documents, spreadsheets, databases or any computer program that allows the use of macro languages.
Macro viruses are basically self-replicating macros.
Macro viruses are spread as the viral macro copies itself, infiltrating files that are opened. As these files are shared, so are the macro viruses. Macro viruses may change or delete file contents. Most macro viruses are written for Microsoft Word, Excel, and Access. Macro viruses are particularly prolific because people exchange documents and spreadsheets more frequently than program files and floppy disks, and macro viruses are very easy to create and modify.