An earlier virus that reprogrammed keyboard keys via the ANSI.SYS system file. For example, an ANSI bomb could remap a function key to format the disk or delete files. To ensure this would happen, the N key was also remapped to the Y key in ANSI.SYS so that when the system prompted "format file: yes/no?" or "format disk: yes/no?" pressing N for No would enter Y for Yes. See
ANSI.SYS and
ANSI.