the computer of a friend in the US Navy, these longer journeys were
rare.
Yet the era of localised, relatively harmless viruses wouldn’t last
long. ‘Computer viruses quickly drifted into a completely different
world,’ said Vespignani. ‘They were mutating. The transmission
routes were different.’ Rather than relying on human interactions,
malware adapted to spread directly from machine to machine. As
malware became more common, the new threats needed some new
terminology. In 1984, computer scientist Fred Cohen came up with
the first definition of a computer virus, describing it as a program that
replicates by infecting other programs, just as a biological virus
needs to infect host cells to reproduce.[7] Continuing the biological
analogy, Cohen contrasted viruses with ‘computer worms’, which
could multiply and spread without latching onto other programs.
Online worms first came to public attention in 1988 thanks to the
‘Morris worm’, created by Cornell student Robert Morris. Released
on 2 November, it spread quickly through ARPANET, an early
version of the Internet. Morris claimed that the worm was meant to
transmit silently, in an effort to estimate the size of the network. But a
small tweak in its code would cause some big problems.
Morris had originally coded the program so that when it reached a
new computer, it would start by checking whether the machine was
already infected, to avoid installing multiple worms. The problem with
this approach is that it made it easy for users to block the worm; they
could in essence ‘vaccinate’ their computer against it by mimicking
an infection. To get around this issue, Morris had the worm
sometimes duplicate itself on a machine that was already infected.
But he underestimated the effect this would have. When it was
released, the worm spread and replicated far too quickly, causing
many machines to crash.[8]
The story goes that the Morris worm eventually infected 6,000
computers, around 10 per cent of the internet at the time. According
to Morris’s contemporary Paul Graham, however, this was just a
guess, which soon spread. ‘People like numbers,’ he later recalled.