The U.S. electrical power grid is still vulnerable to attack, and regulatory bodies don't have the authority they need to respond quickly to new threats, top officials told a Congressional committee today.

In testimony before the House Subcommittee on Emerging Threats, Cybersecurity, and Science and Technology, the heads of the Federal Energy Regulatory Commission (FERC) and the North American Electric Reliability Corp. (NERC) both conceded that there are significant flaws in the current process for identifying and responding to attacks on the power grid.

"There is some risk" that a single cyber attack could cause a major power disruption on a wide geographic scale, said Joseph Kelliher, chairman of FERC.

The testimony was given on the same day that the Government Accountability Office issued a public report citing 19 major flaws in the cyber security defenses of the Tennessee Valley Authority, one of the nation's largest electric utilities. The GAO also issued a separate, limited-access report that cites 73 additional vulnerabilities at the TVA.

The crux of the problem is that America's utilities, many of which are operated as private businesses, don't have a structured method for responding quickly to new cyber threats, the witnesses testified. When the Department of Homeland Security identifies an attack, NERC can issue a warning and guidance on what to do about it, but the response by individual utilities is purely voluntary.

FERC, for its part, can put out a call for mandatory IT standards that would force all utilities to implement specific defenses against an attack. However, because FERC is not an official government agency, it must post such a request for a long period of public comment, effectively giving attackers a long window of opportunity to exploit the vulnerability before it is uniformly remediated.

"This is one of the things I see in this committee that keeps me up at night," said James Langevin, chairman of the subcommittee. "I am not confident that everything that needs to be done is being done."

Several members of the subcommittee also expressed consternation at testimony given by NERC last October, in which the commission testified that 75 percent of the identified vulnerabilities had been addressed -- and then failed to deliver data to support that assertion.

"What do you think we are, a bunch of jerks?" asked Rep. Bill Pascrell. Pascrell called for NERC to be held in contempt of the committee for delivering misleading testimony about the state of the utilities' cyber defenses.

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