While Target confirmed today that debit PIN numbers were compromised in a massive cyber attack that put customer data on the black market, the FBI is currently investigating an apparent real-world attack on a San Jose power plant from earlier this year. According to Foreign Policy, it's possible that two unidentified gunmen fired "military-style" weapons at transformers at the San Jose PG&E substation in an act some see as sabotage.
The gunmen attacked the facility on April 16th, taking down ten transformers and three transformer banks at the time. Though the resulting outages were minor, they did briefly knock out landline, 911, and cell service. Initially, the raid was seen as an act of vandalism, but investigators now worry that the attack shows a level of sophistication that might signal future ones. However, though surveillance footage was released in an effort to track down the gunmen, no one has stepped forward.
There are ways to take down the grid
The incident has raised concerns that the US government is not adequately protecting its physical infrastructure, focusing increasingly on cyber crime. "There are ways that a very few number of actors with very rudimentary equipment could take down large portions of our grid," John Wellinghoff, chairman of the Federal Energy Regulatory Commission, said at a recent event sponsored by Bloomberg. "I don't think we have the level of physical security we need." However, although even nuclear power plants are known to be vulnerable, a concerted, militarized effort to attack them has yet to take place.
Update, February 4th: The Wall Street Journal has more details.