are we so vulnerable to such disruption? The very genius of the internet is the fact that it connects everything. But this is also its Achilles' heel. If a car breaks down, it will affect five or six people at most. Yet if the central computer controlling the traffic lights of London goes belly up, an entire city hits gridlock. And these networks are easier to break than you might think. In 2008, a crackdown by the Pakistan Telecommunication Authority on YouTube, over anti-Islamic videos that were hosted there, resulted in much of the world losing access to the site. The censor had typed in the wrong instructions, and rather than blocking the site sent hundreds of millions of requests for it flooding to Pakistan Telecom's network. Two years later, in 2010, Waddell & Reed Financial of Kansas attempted to execute an algorithmic sale of 75,000 futures contracts on American stock markets, valued at $4.5 billion. Its poorly written instructions triggered havoc, with automated trading systems misinterpreting the trade and wiping 1,000 points off the Dow Jones Industrial Average within minutes. The real potential for disaster, however, can be seen in three separate events, all of which took place in 2007. In the first, Los Angeles Airport, one of the biggest in the world, seized up after cables supplying the internet to the US Department of Homeland Security burnt out. Twenty thousand passengers were penned into an area between tarmac and immigration for almost 24 hours before technicians were able