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Electronic attacks on banks, retailers and oil companies have amplified calls to fortify the U.S.'s aging electric grid, which some believe is more vulnerable than ever to terrorism. For years, the more than 3,000 utilities that provide the United States with electricity have been the focus of security concerns. Yet in the shadow of the 13th anniversary of the Sept. 11 terror attacks, a growing threat from terrorists and multiple assaults on U.S. companies, risks to the energy grid appear to be multiplying. Read MoreDouble threat: US grid vulnerable on two fronts

A sophisticated attack on the energy grid "is real and needs to be addressed urgently," said James Woolsey, chairman of the Foundation for the Defense of Democracies, in an interview. "A hacker could very seriously damage the grid."

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For their part, utilities and regulators insist they are on the case, especially in the wake of two separate physical breaches at a Pacific Gas & Electric (PG&E) Silicon Valley substation that have heightened security fears within the industry. A PG&E spokesman told CNBC that the utility company plans to spend $100 million over the next three years "to enhance security at our critical facilities."

The Energy Policy Act of 2005 granted the Federal Energy Regulatory Commission (FERC) responsibility to work in tandem with power companies to improve the grid's reliability, and enforce standards to keep the power flowing in the event of any contingency.

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In response to an inquiry from CNBC, Cheryl LeFleur of FERC said her agency "works continuously with the electric industry to assess and respond to the threats posed by physical attacks, cyber-intrusions, and severe weather," using mandates and voluntary initiatives.

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