>the idea of self-replicating software was unusual

floppy based viruses were well established and quite common

True. I should probably have qualified that to something like "independently self-replicating". Floppy-disk based viruses obviously still required humans in the transmission path, whereas the Morris Worm and its successors were novel in that they used the internet and worked without human intervention.

Memories of adding an illicit McAffee to autoexec.bat on my boot floppies...

Yes. We ran non networked, Mac computer rooms at university, and having a good antivirus was an absolute must. Infections spread through floppies.

The Mac's ease of use as opposed to the PC made it also the juiciest virus target.