The early architects of the internet did not want it to kill anybody. In cyber security expert Bruce Schneier’s new book, David Clark, a professor at the Massachusetts Institute of Technology, recalls their philosophy: “It is not that we didn’t think about security. We knew that there were untrustworthy people out there, and we thought we could exclude them”.

Schneier describes how the internet, developed as a gated community, is now a battleground where these untrustworthy people cause great harm: harnessing computers to kill by crashing cars, disabling power plants and perhaps, soon enough, using bioprinters to cause epidemics.

The clumsily-named internet of things, which Schneier rechristens the barely more elegant Internet+, is growing fast: between 20bn to 75bn devices could be online by 2020, depending on the estimate. This mushrooming hands more power to hackers, while cyber defenders struggle to protect the internet.