My piece in today’s Observer.

In 1971, Bob Thomas, an engineer working for Bolt, Beranek and Newman, the Boston company that had the contract to build the Arpanet, the precursor of the internet, released a virus called the "creeper" on to the network. It was an experimental, self-replicating program that infected DEC PDP-10 minicomputers. It did no actual harm and merely displayed a cheeky message: "I'm the creeper, catch me if you can!" Someone else wrote a program to detect and delete it, called – inevitably – the "reaper".

Although nobody could have known it 40 years ago, it was the start of something big, something that would one day threaten to undermine, if not overwhelm, the networked world…