An unsolved sniper attack last year on an electrical power substation in California that knocked out 17 giant transformers has mobilized industry leaders to beef up physical security at these vital installations. The incident also has some experts worried that parts of the U.S. power grid are similarly vulnerable.
On April 16, 2013, attackers cut fiber optic cables in an underground vault and then fired more than 100 rounds from at least two high-powered rifles on Pacific Gas and Electric's Metcalf power transmission station near San Jose, California.
The attack did not cause major power disruptions because officials were able to reroute electricity remotely during the 27 days it took to repair the installation and get it back on line, according to PG&E spokesman Brian Swanson.
The California power utility had never previously experienced such a large-scale act of aggression.
"Ever since, we've been working very aggressively to improve substation security, not just at Metcalf but throughout our system," Swanson said.
"Its not just PG&E acting alone. The utility industry as a whole is working with stakeholders like the Edison Electric Institute, with policy makers, with government and law enforcement officials at all levels," he added.
An FBI investigation is ongoing, but has so far resulted in no arrests. Swanson declined to speculate on the perpetrators' identity or possible motive.
Criminal Act or Domestic Terrorism
Security experts told VOA the incident was most likely either a criminal act committed by a disgruntled employee or - far more dangerous - an example of domestic terrorism.
"This was likely either a former, or even a current employee, possibly an insider, someone that's left who's disgruntled, on the criminal side," said Daryl Johnson, a consultant with DT Analytics, a Washington, DC-based security firm.
"[Or], on the terrorism side, it could be a domestic, non-Islamic terrorist, or possibly a home-grown Muslim extremist," he said.
A disparate array of domestic groups - ranging from "green anarchists and environmental extremists" that oppose the use of fossil fuels to "anti-government militias" hoping to sow terror and undermine federal authority - could have been responsible, said Johnson.
"We've seen 'chatter' on both of those movements that indicate they're interested in targeting infrastructure," he said.
"And we've actually had cases where people in both the militia-anti-government movements as well as the anarchist-environmental extremist movements have been arrested for targeting critical infrastructure or actually sabotaging the electrical grid," Johnson said.
In December, Rep. Henry Waxman (D., Calif.) told a Federal Energy Regulatory Commission oversight hearing that the April incident was hardly the only threat facing America’s electricity grid.
"A few months ago in Arkansas, there were multiple attacks on power lines and grid infrastructure that led to millions of dollars in damage and brief power outages. Independent engineers recently discovered a new cyber vulnerability in the software used by many electric grid control systems," Waxman said.
As part of its detailed investigation of the Metcalf attack published Wednesday, the Wall Street Journal quoted former FERC chairman Jon Wellinghoff as saying it was "the most significant incident of domestic terrorism involving the grid that has ever occurred" in the United States.
The event has received little public attention until now, although as word of the attack spread through the utility industry, some companies moved to review their security policies.
FERC has also initiated an unusual public awareness campaign, holding briefings on the physical security of electricty substations in cities throughout the U.S.