XM.Laroux is a virus first discovered in July 1996 in Africa and Alaska and is the first working Excel macro virus found in general circulation. The actual virus code consists of two macros called Auto_Open and Check_Files. The macros are stored in a hidden datasheet named "laroux."
In infected spreadsheet files (Excel workbooks), the "laroux" datasheet is not readily visible (it is hidden). When an infected spreadsheet is first opened on a system, the Auto_Open macro is automatically run by Excel, which in turn runs the Check_Files macro. This happens each time a worksheet is activated.
The Check_Files macro then copies the worksheet with the virus code into a spreadsheet file stored in the Excel startup directory named "Personal.xls." (By default, this directory is \MSOffice\Excel\XLStart.) Personal.xls is the "global macro spreadsheet;" macros stored there are automatically available to all other Excel spreadsheets on the system. Copying these macros to Personal.xls enablesthe infection of all other spreadsheets opened or created on the infected system in the future.
XM.Laroux contains no deliberately destructive payloads: it exists only to replicate. XM.Laroux only "works" on Microsoft Windows operating systems using Excel versions 5 and 7. It does not work in the Macintosh environment.
XM.Laroux is written in English.
XM.Laroux was discovered in a limited distribution and has showed no sign of rapid spread.
