So, in order to implement macros viruses which can change its contents, hackers have to create another macro which fulfills the task to modify the content of the virus. However, this type of macro viruses is not widespread. Indeed, hackers frequently choose to do macro viruses because they are easy and quick to implement. Making a polymorphic macro requires a lot of knowledge of the WordBasic language (it needs the advanced functionalities) and more time than a "classic" macro virus. Even if a hacker were to make a polymorphic macro, the polymorphism needs to be done, so, the document needs to update and the update can be visible to a user.
so in order to implement macros viruses which can change its contents hackers have to create another macro which fulfills the task to modify the content of the virus however this type of macro viruses is not widespread indeed hackers frequently choose to do macro viruses because they are easy and quick to implement making a polymorphic macro requires a lot of knowledge of the wordbasic language (it needs the advanced functionalities) and more time than a "classic" macro virus even if a hacker were to make a polymorphic macro the polymorphism needs to be done so the document needs to update and the update can be visible to a user