In the early years floppy disks (removable media) were in fact the prevalent method used to spread viruses. Bulletin boards and online software exchange systems emerged as major channels for the spread of viruses in the late 80s. Ultimately of course, the internet in all its forms became the major source of infection.
Our timeline for PC Virus history, is as follows (work in progress):
The first externally released virus is thought to be 'Elk Cloner', written by Rich Skrenta. It infected Apple DOS 3.3 computers, and spread via floppy disk.
The term 'computer virus' begins to emerge. This is often credited to Fred Cohen of the University of Southern California.
Early PC viruses start to appear. One of the first, emerging from Pakistan, is known as the 'Brain' and is a 'boot sector' virus (floppy disk).
The first 'file' viruses begin to appear (largely affecting the essential system file command.com).
The ARPANET worm, written by Robert Morris, disables approx 6,000 computers on the network.
The well known (at the time) Friday the 13th virus is released in this year.
The Cascade virus, thought to be the first encrypted virus, is discovered. is found
The AIDS trojan appears. It was fairly unique at the time because it demanded payment for removal.
Anti-virus software begins to appear
Norton Anti-Virus software is released by Symantec.
The first widely spread polymorphic virus (one which changes its appearance as it spreads), "Tequila", is released.
Well over 1,000 viruses are now thought to exist.
The first major virus hoax, known as "Good Times" surfaces
The first major 'Word' virus emerges, known as "Concept"
The "Melissa" virus, written by David L. Smith, infects countless thousands of PCs (estimated damage = $80 million). It replicates by sending copies of itself to addresses in the
Microsoft Outlook address book. The author is subsequently jailed for 20 months.
In May of this year, the 'I Love You' virus, written by a Filipino student, infects
millions of PCs. It is similar to "Melissa" but sends passwords back over the network.
In July, the Code Red worm infects thousands of Windows NT/2000 servers, causing $2 billion in damages (estimated)
In January the "Slammer" worm spreads at the fastest rate thus far, and infects hundreds of thousands of PCs.