The Pentagon is building a virtual city that will enable government hackers to practice attacking and defending the computers and networks that increasingly run the world’s water, power and other critical systems. To reinforce the effect of those attacks, the cyber-range, known as “CyberCity,” will include a scale model of buildings and other facilities that will light up when attacks have been successful. …

Think of it as something like the mock desert towns that were constructed at military facilities to help American soldiers train for the war in Iraq. But here, the soldier-hackers from the Air Force and other branches of the military will practice attacking and defending the computers and networks that run the theoretical town. In one scenario, they will attempt to take control of a speeding train containing weapons of mass destruction. …

CyberCity provides insight into some of the Pentagon’s closely guarded plans for cyber war. It also reflects the government’s growing fears about the vulnerabilities of the computers that run the nation’s critical infrastructure. Last month, Defense Secretary Leon E. Panetta said that digital attacks “could be as destructive as the terrorist attack on 9/11” and virtually paralyze the country. …

Behind those fears is an unsettling reality: Networks in the United States will remain vulnerable to attacks for the foreseeable future because no one understands cyberspace well enough to ensure security.