The Excel Call security hole allows the "bad guys" to hid malicous programs inside of an Excel spreadsheet file. The security hole exists because the Excel call function can make arbitrary Windows system calls from inside of a spreadsheet without any security warnings.

The demo spreadsheet tests if your system has the security hole or not. If you click on the "Demo" button below, Excel will be started on your system and a harmless spreadsheet will be loaded from the Web. This spreadsheet contains a call function which puts up a simple message using the Windows MessageBoxA system call.