A macro virus usually infects the master document template, which acts as a standard for all newly created or modified documents. In Microsoft Word, the master document template is a file called normal.dot. Once this file is infected, all documents created or opened after its infection are tainted by the macro virus. To warn users of the threat of macro viruses, Microsoft Office applications have a macro warning dialog box that pops up when the program thinks it finds a macro virus. Macro viruses commonly disable this warning to allow infected documents to open after the system has been infected.
Macro viruses can be very destructive.
Script Viruses S cript viruses use interpretative programming languages. These programming engines do what the scripts tell them to do. E-mail clients such as Outlook and Outlook Express are able to run VBS scripts. The Windows Scripting Host software also allows VBS scripts to run. Windows 98 and Windows 2000 machines have this installed by default Some Windows 95, and Windows NT PCs may also have this software installed.