CDEF infects the hidden Desktop file used by the Finder. If the Macintosh is infected with the CDEF virus, floppy disks are infected as soon as they are inserted or mounted. If an infected floppy disk is inserted in the computer, the virus will infect any mounted hard disk.
In some cases, the system beeps when a new Desktop file is infected. CDEF does not display any common symptoms, it simply spreads. Rebuilding the Desktop removes the virus. To rebuild the Desktop, press and hold Command-Option while inserting a floppy disk or, for hard disks, while starting the computer.
