AP file photo Washington's Metro trains shut down in a previous mock disaster.

WASHINGTON — In the middle of the biggest-ever "Cyber Storm" war game to test the nation's hacker defenses, someone targeted the very computers used to conduct the exercise.

The surprising culprit? The players themselves, the same government and corporate experts responsible for detecting and fending off attacks against vital computer systems, according to hundreds of pages of heavily censored files obtained by The Associated Press. Perplexed organizers sent everyone an urgent e-mail marked "IMPORTANT!" instructing them not to probe or attack the game's control computers.

"Any time you get a group of (technology) experts together, there's always a desire, Let's show them what we can do,'" said George Foresman, a former senior Homeland Security official. "Whether its intent was embarrassment or a prank, we had to temper the enthusiasm of the players."

The exercise was a big deal for all concerned. The $3 million, invitation-only war game simulated what the U.S. describes as plausible attacks over five days in February 2006 against the technology industry, transportation lines and energy utilities by anti-globalization hackers. The government is organizing "Cyber Storm 2."

Among the mock disasters confronting officials in the previous exercise: Washington's Metro trains shut down. Seaport computers in New York went dark. Bloggers revealed locations of railcars with hazardous materials. Airport control towers were disrupted in Philadelphia and Chicago. Overseas, a mysterious liquid was found on London's subway.

The Homeland Security Department ran the exercise, with help from the State Department, Pentagon, Justice Department, CIA, National Security Agency and others.

How did they do? Reviews were mixed. Companies and governments worked successfully in some cases. But key players didn't understand the role of the premier U.S. organization responsible for fending off major cyber attacks, called the National Cyber Response Coordination Group, and it didn't have enough technical experts. Also, the sheer number of mock attacks complicated defensive efforts.

The upcoming "Cyber Storm 2" in March also will simulate electronic attacks against chemical plants and communication lines, and include targets in California, Colorado, Delaware, Illinois, Michigan, North Carolina, Pennsylvania, Texas and Virginia.