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Understanding Macro Viruses

You've probably heard a lot of talk about viruses that your computer can catch from other computers on a network, the Internet, or disks. But what if your macros contain viruses? Viruses can contaminate your macros if the workbook is from an unsecure network or Internet site.

To prevent your computer from becoming contaminated with macro viruses, you can display a warning message whenever you try to open a workbook that contains a macro. This warning message always appears whether or not the macro actually has a virus. When the message displays, try to make sure that you know and trust the source of the workbook before you continue.

To check workbooks for macro viruses and display that warning message, choose Tools, ...