"About once every four days, part of the nation's power grid — a system whose failure could leave millions in the dark — is struck by a cyber or physical attack, a USA TODAY analysis of federal energy records finds.

Although the repeated security breaches have never resulted in the type of cascading outage that swept across the Northeast in 2003, they have sharpened concerns about vulnerabilities in the electric system. A widespread outage lasting even a few days could disable devices ranging from ATMs to cellphones to traffic lights, and could threaten lives if heating, air conditioning and health care systems exhaust their backup power supplies.

Some experts and officials fear the rash of smaller-scale incidents may point to broader security problems, raising questions about what can be done to safeguard the electrical grid from an attack that could leave millions without power for days or weeks, with potentially devastating consequences."

Steve Reilly reports for USA Today March 24, 2015. [2]