X97M/VCX is a Microsoft Excel 97 macro virus.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
X97M/VCX.A activates when an infected workbook is closed or a worksheet is deactivated.
It creates a temporary file, "C:\Windows\System\Xlscan.386", and disables the macro virus protection via registry. Then the virus creates a new workbook, infects it and saves it to the Excel's startup directory with a name "Xlscan.xls". After that it infects every workbook using the temporary file.
It also creates eleven additional files to "C:\Windows\System" directory every time it gets control. Ten of these files will named after the current date and time, a number from 1 to 10 and the extension ".VCX"; while the last file will have a constant name "Xlscan.idx".
X97M/VCX.B is a slightly modified variant of X97M/VCX.A.
X97M/VCX.C is a modified variant of X97M/VCX.A. The file names are changed: Temporary file is "C:\Windows\System\MsOffice.386" and the file created to Excel's starup directory is "MsOffice.xls". Also the last file created to the Windows' System directory has a different name, "MsOffice.idx".
Description Created: Analysis: Sami Rautiainen, F-Secure