Is the Internet facing "the cyber equivalent of the World Trade Center attack?" According to a former security chief, the U.S. has already received its "9/11 warning" for a cyber-attack that could take down the banks, power and ultimately cripple the economy.

Former U.S. Intelligence Chief John "Mike" McConnell, who served under President Clinton, George W. Bush and Barack Obama, told the Financial News the U.S. has already been warned about a huge potential cyber threat that could have a tremendous negative impact on the country.

"We have had our 9/11 warning. Are we going to wait for the cyber equivalent of the collapse of the World Trade Centers?" said McConnell, calling the warnings a wake-up call to businesses and political leaders.

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McConnell detailed what a large-scale cyber-attack could mean for the country.

"All of a sudden, the power doesn't work, there's no way you can get money, you can't get out of town, you can't get online, and banking, as a function to make the world work, starts to not be reliable," he said. "Now, that is a cyber-Pearl Harbor, and it is achievable."

Although McConnell believes a terrorist group might not be able to carry out such an attack right now, sophisticated tools could fall into the wrong hands in the future.

McConnell is currently vice chairman at Booz Allen Hamilton, a technology consulting firm which contracts with private businesses as well as the federal government.

The news comes several months after a series of cyber-attacks targeted major banks such as JPMorgan Chase and Bank of America and crippled computers at a Saudi Arabian oil company Saudi Aramco in August.

In November, U.S. Secretary of Defense Leon Panetta spoke at a meeting of the Business Executives for National Security and told leaders the events signaled "a significant escalation of the cyber threat."

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