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Parts of the U.S. power grid are attacked online or in person every four days, according to an analysis of federal energy records.
The finding raises questions about the electrical system’s physical and cyber defenses at a time of rising threats.
USA Today, which analyzed federal data and surveyed more than 50 electric utilities, described the power grid as vulnerable to a major outage that could affect millions.
While a cyberattack has not yet caused a major loss of power, the mechanisms guarding the grid undergo small hacks multiple times a week, the paper reported.
"There are probes that happen all the time,” Scott Aronson, senior director of national security for the Edison Electric Institute, told the paper.
“Adversaries are essentially looking for weaknesses in a network. I've heard people say millions [of attacks occur] a day.”
Available federal data points to a rise in cyberattacks against the energy sector, though the definition of “attack” is fuzzy and may not include smaller incidents.
The Department of Homeland Security was alerted to 151 energy-related “cyber incidents” in 2013, up from 111 in 2012 and 31 in 2011, USA Today reported.
A sophisticated team of hackers could find ways to disable major pieces of the U.S. grid through targeted attacks of critical nodes, experts said.
Power plants are also seen as highly vulnerable to physical violence.
Critical equipment is often protected only be a chain-link fence and a few security cameras, and suspects have never been identified in the hundreds of attacks on electrical infrastructure that have taken place since 2011, the paper reported.