It has already provided the script for at least one blockbuster Hollywood movie, but if hackers managed on a busy day to shut down train networks, disrupt airport control systems and cause huge traffic jams in major cities, there would be no Bruce Willis around to come to the rescue.It has now been revealed that the US Government held a major exercise in cyberspace two years ago to test its defences against any such attack, and it plans another later this year.
http://www.abc.net.au/news/stories/2008/02/02/2152872.htm