According to Sophos, WM97/Thursday-C is an optimized variant of WM97/Thursday. For those who may have forgotten, WM97/Thursday is a simple macro Word virus.

WM97/Thursday-C is set to trigger Dec. 13, 1999, when it’s programmed to delete all files and subdirectories on a victim’s C: drive. Sophos has an IDE file available for download on its Web site . The virus also operates with the alias W97M/Thus.C.