What changed?
Floppy disks were both storage and a way to carry software between personal computers. Many systems started from removable media, making the disk’s startup area an important security boundary.
How it spread / worked conceptually
At a conceptual level, a disk that carried altered startup information could expose the next computer when the disk was used there. Moving a disk—not a network connection—was the propagation path.
Why it mattered
It showed that ordinary sharing practices could carry unwanted software across a growing PC culture.
Representative historical examples
Elk Cloner (1982) is often cited as an early personal-computer virus. Brain (1986) became historically significant as an early IBM PC-compatible boot-sector virus.
What defenders learned
Users and technicians learned to treat removable media as a trust boundary and to check startup media before use.
What changed next?
As PCs became more common, malware moved beyond boot media and began targeting files and memory.