"The whole energy system is being run on a cyber system," Abbie Layne, project manager at the Department of Energy's National Energy Technology Laboratory, told an electricity industry conference in Houston.
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"You can do a lot of damage just through a quick strong strike to that cyber system," she said.
A successful attack on computer networks that support the electricity system could have devastating economic impact if a "cascading" shutdown hobbled the grid of power lines, possibly shutting off the lights in a region.
"If we lose this infrastructure...we could have a lot of damage to our economy," Layne said.
Energy industry experts believe that while a threat to oil tankers, pipelines or power plants remains a frightening prospect, there is no evidence those sites have been targeted.
"To this point, there have been no specific threats to the industry," Gary Gardner, chief information officer at the American Gas Association, told the conference.
Although manuals describing methods to attack natural gas systems were discovered by U.S. forces during raids on suspected Taliban and al Qaeda bases in Afghanistan, Gardner said the industry did not believe a violent attack against an energy installation was the most likely scenario.
Security for power plants, oil refineries and the vast network of natural gas and oil pipelines comes under the jurisdiction of a former Department of Energy unit that was recently moved to the newly created Department of Homeland Security.
Another Homeland Security division handles "cyber," or computer network, security, but that unit remains without a leader despite an extensive search, according to Harris Miller, a security expert and president of the industry umbrella group Information Technology Association of America.
"There is nobody in the Department of Homeland Security in charge of cyber-security," Miller said. "It's a little scary."
The energy sector does have some safeguards to prevent interlopers from gaining access to sensitive systems, Miller said, but it probably falls "in the middle of the pack" compared with other industries.
Still, even the financial industry, which boasts the most secure networks, can be hit by hacker attacks, Miller said.
In January, the "slammer worm" virus infiltrated financial companies' computers systems despite widely available preventive software, and last month hackers accessed about 8 million credit card numbers from a processing company.