From Symantec Corporation
As new threats emerge, Symantec immediately builds new protection updates and makes them available for download on a subscription basis. If your subscription has expired, click here.
The Norton AntiVirus engine is common to the Norton AntiVirus, Norton Internet Security, and Norton 360 products. You can update these products using definitions shown below as supporting Norton AntiVirus.
End of Life for Floppy Disk Definition Sets
Beginning Thursday, August 18th, 2005, US Pacific Time, Symantec will no longer be releasing definitions sized to fit a set of standard 1.44 MB floppy disks. Due to the increasing size of virus definitions files and the supplanting of floppy disks with other technologies, we will no longer be releasing definitions in this format. Definitions will continue to be made available through all other current methods.
Norton Definitions updates, released on October 10, 2016