How Early Viruses Spread from Computer to Computer

In the mid-to-late 1980s, data was most often transferred from computer to computer by using floppy disks and so-called bulletin board systems (BBSs), managed online locations that were the forerunners of today’s Web sites.

Stowing away on floppy disks

Even without using the Internet, people in offices where PCs were used traded and circulated programs, documents, and spreadsheets — not to mention jokes, games, filthy pictures, and so forth. The standard method was sneaker net — walking up to another person and handing over a floppy disk.

In those early days, viruses spread relatively quickly. Because few people had antivirus programs, there was little to stop a virus from spreading from computer to computer. Like hobos on trains and stowaways on ships, viruses were unwelcome and mostly unnoticed  passengers that rode for free and left their mark in some way.

Sneaking in via BBSs

Before the World Wide Web, BBSs were the precursors to the way we use the Internet these days. Reached via dial-up modems, BBSs contained a variety of features such as limited e-mail (you could only send messages to other users of that particular BBS), file uploading and downloading, games, and well, bulletin boards (where you could stick any messages you wanted seen by other BBS users), and so forth.

Modem technology was primitive, with speeds far slower than today’s modems. Common modem speeds were 1200, 2400, and 4800 kilobits per second — any faster and the rawhide thongs would break (just kidding) — a mere fraction of the 56000 bits per second (56 kbps) available now. But communication with a BBS consisted of characters only: words, numbers, and punctuation — no graphics. Of course, that also meant no time was wasted loading banner ads, distracting animations, or lame design (any of which can show up on today’s Web sites, so the slower modems weren’t all that bad).

At the time, going online wasn’t all that common, so BBSs attracted users by amassing a rich collection of programs and files — and making those available for download. Often a BBS would award download privileges only to users who had uploaded a certain minimum amount of programs and data, thereby enriching the BBS’s collection of goodies. Those file-upload-and-download areas became a big free ride for viruses.

Most BBSs had a policy of forbidding the uploading and downloading of commercial software, but it was difficult to police, and BBS operators frequently looked the other way. A number of BBSs did contain illegal copies of commercial software; relatively few perpetrators were caught and prosecuted. But what better lure than something-for-nothing — and hey, how about a little something extra? Some of those illegal copies contained (you guessed it) viruses. But I digress.

My point is that viruses would attach themselves to computer programs on a user’s system, and if that user uploaded the infected program to a BBS, then anyone who later downloaded and ran that program would subsequently become infected.

As a result, viruses spread faster and over greater distances than they could with floppy disks. Why should an ambitious virus wait for a person to infect one other person at a time in real-world offices (or between friends and among computer hobbyist club members) when the Internet made thousands of potential hosts available?