The following information summarizes how macro (macro: An action or a set of actions that you can use to automate tasks. Macros are recorded in the Visual Basic for Applications programming language.) virus protection works under each setting on the Security Level tab in the Security dialog box (Tools menu, Macros submenu) under different conditions.
A macro virus is a type of computer virus (virus: A computer program or macro that "infects" computer files by inserting copies of itself into those files. When the infected file is loaded into memory, the virus can infect other files. Viruses often have harmful side effects.) that is stored in a macro (macro: An action or a set of actions that you can use to automate tasks. Macros are recorded in the Visual Basic for Applications programming language.) within a Microsoft Office Visio file, ActiveX control, COM add-in (add-in: A supplemental program that adds custom commands or custom features to Microsoft Office.), or Visio add-on (add-on: A program that extends the Visio application through Automation references to Visio objects, methods, and properties.).
Note Because macros can contain viruses, be careful about running them. Among the precautions you take, be sure to run up-to-date antivirus software on your computer, use digital signatures, and maintain a list of trusted sources of macros. Visio cannot scan a disk, disk drive, or network drive to find and delete macro viruses. If you want this kind of protection, you must purchase and install specialized antivirus software. Visio does, however, display a warning message whenever you open a document that contains macros that might contain a virus.
Only macros installed in trusted locations are allowed to run. All other signed and unsigned macros are disabled. You can disable all macros entirely by setting your security level to Very High and disabling macros installed in trusted locations. To disable macros installed in trusted locations, click Tools, point to Macros, and then click Security. On the Trusted Publisher tab, clear the Trust all installed add-ins and templates check box. This disables all COM add-ins and third-party add-ons, as well as macros.
When security it set to low, all macros are treated equally regardless of origin or certificate status. With low security, you receive no prompt or signature validation and macros are automatically enabled. Use this setting only if you are certain that all macros in your files are from trusted sources.