As reported by Taylor Armerding at NetworkWorld:
Candid Wueest, a researcher for security firm Symantec...reported that there were an average of 74 targeted cyberattacks per day between July 2012 and June 2013, with the energy sector accounting for 16.3% of them, which put it in second place behind government/public sector at 25.4%.
The U.S. government's Department of Homeland Security (DHS) reported last year that its Industrial Control Systems Cyber Emergency Response Team (ICS-CERT) responded to more than 200 incidents between Oct. 2012 and May 2013 -- with 53% aimed at the energy sector.
There have, so far, not been any successful catastrophic attacks on the grid, and there is ongoing debate about how high the risk is for what both former Defense secretary Leon Panetta and former Homeland Security secretary Janet Napolitano called a "cyber Pearl Harbor" attack.
Some experts contend that while the risks are real and should cause concern, they are unlikely to cause catastrophic, long-term damage. Others say the nation's economy could be paralyzed for a number of months to more than a year while critical infrastructure (CI) systems are rebuilt.
Of course, while loss of electricity would be a major to complete disruption to modern society, another catastrophic aspect, at atomic reactors and other nuclear facilities, such as high-level radioactive waste storage pools, could be releases of hazardous radioactivity if safety and cooling systems are disabled by a cyber-attack.