Macro viruses are viruses in the classic sense. They deserve special attention because of how they function and because they are extremely common. Macro viruses exploit the capabilities of macros in applications such as Microsoft Office. Macros are typically used to automate tasks and sometimes to create sophisticated templates. But their scripting power (and the fact that Office macros can often utilize all the Office applications under Windows) can make macros into prime and easy-to-maliciously code tools for creating viruses. Macro viruses are no less dangerous than other viruses, although they often infect only file types that the host application(s) can edit.
Macro viruses have another trick up their sleeve: they can be cross-platform. The Mac OS X versions of Office include support for many macro scripting elements to provide interoperability with documents and templates created on Windows computers. This means that macro viruses can carry some danger to Mac users. Typically, however, that danger is much more limited because the macro support is not as closely integrated into Mac OS X as Office’s capabilities are with Windows. However, Mac users can have macro viruses residing in files they receive from Windows users and can pass them on. It is possible that some effects, such propagating to other files, can occur.