Passengers may have largely deserted America's rails but freight trains remain vital to America's economic well-being. Like most other pieces of modern infrastructure the railways are controlled by complex digital systems. And there are growing fears that these computers could fall prey to cyber-attack, as could all the other electronic support systems on which modern society now depends. Last year the then US defence secretary Leon Panetta spoke of the possibility of a possible "digital Pearl Harbor"; a massive attack that might target US transport infrastructure and utilities.
Just a few weeks ago in his State of the Union address President Barack Obama added his own warning. "We know hackers steal people's identities and infiltrate private emails," he said. "We know foreign countries and companies swipe our corporate secrets," he went on, "now our enemies are also seeking the ability to sabotage our power grid, our financial institutions, our air traffic control systems."
Key services
Hundreds of private companies are springing up to respond to the possibility of a digital doomsday. The stakes are high as Shawn Henry told me. "Other than a weapon of mass destruction going off in a major city," he says, "the cyber-threat is one of the most significant challenges that we face." Mr Henry is a former executive assistant director of the FBI - he was responsible for its cyber-investigations worldwide. He is now president of Crowdstrike, a company which helps firms protect against hackers. "Everything we do day-to-day relies on cyber-communications," he said. "All of our data that's being pushed to the network or financial services sector, our critical infrastructure, our electric power grid, our water systems. "We know with certainty that there are groups that are actively seeking to target and harm the western world through attacks on the cyber-network. "If that happens I think we are going to suffer some significant consequences."
Hurricane Katrina in 2005 showed how quickly a sophisticated society can start to break down once key services are destroyed. The Secretary of Homeland Security at the time of the hurricane, Michael Chertoff, told me that the threat from cyber-attack is very real. He said: "Even now as we speak there are millions of attacks every day on infrastructure, simply stealing information or stealing intellectual property. "Now, the same capability that allows somebody to do that is a capability that allows someone to be destructive. So yes it is a distinct possibility that systems that are connected to the internet, if they control operations, could be damaged or destroyed."
Cyber City