The U.S. government has concluded its “Cyber Storm” wargame — its biggest-ever exercise to test how it would respond to devastating attacks over the Internet from anti-globalization activists, underground hackers and bloggers.

Parts of the worldwide simulation, conducted in mid-February, challenged government officials and industry executives to respond to deliberate misinformation campaigns.

The Internet survived, even against fictional abuses against the world's computers. Experts depicted hackers who shut down electricity in 10 states, failures in vital systems for online banking and retail sales, infected computer disks mistakenly distributed by commercial software companies and critical flaws discovered in core Internet technology.

“We will review the lessons learned through this exercise to better prepare in the event of a national cyber incident,” says Jimmy Kuo, research fellow, for McAfee AVERT Labs, which was a participant in the event.

Some mock attacks were aimed at causing a “significant cyber disruption” that could seriously damage energy, transportation and health care industries and undermine public confidence, George Foresman, an undersecretary at the Homeland Security Department, told The Associated Press.

Government officials from the United States, Canada, Australia and England and executives from Microsoft, Cisco, Verisign and others said they were careful to simulate attacks only using isolated computers, working from basement offices at the Secret Services headquarters in downtown Washington.

The Department of Homeland Security promises a report on results from the exercise by summer.

More than 115 government agencies, companies and organizations participated, including the White House National Security Council, Justice Department, Defense Department, State Department, National Security Agency and CIA.