Simply by reading this, you have allowed me to hijack your thoughts, each word leaping from my mind to yours. I can even conjure mental images against your will – quick, don't think about a pink elephant! Whatever you do, don't imagine it! Thankfully, there are limits to what I can do to you with words and ideas alone. What if there were a phrase so powerful that I could use it to turn your own mind against you, to the point of death?

Neal Stephenson's 1992 novel Snow Crash is the book that launched a thousand startups. It was the first book to use the Hindu term avatar to describe a virtual representation of a person, it coined the term "metaverse", and was one of Mark Zuckerberg's pieces of required reading for new executives at Facebook a decade before he changed the focus of the entire company to attempt to build Stephenson's fictional world in reality. The plot revolves around an image that, when viewed in the metaverse, hijacks the viewer's brain, maiming or killing them. In the fiction of the world, the image crashes the brain, presenting it with an input that simply cannot be correctly processed. Perhaps the first clear example came four years earlier, in British SF writer David Langford's short story BLIT, which imagines a terrorist attack using a "basilisk", images which contain "implicit programs which the human equipment cannot safely run". In a sequel to that story, published in Nature in 1999, Langford draws earlier parallels, even pulling in Monty Python's Flying Circus, "with its famous sketch about the World's Funniest Joke that causes all hearers to laugh themselves to death".