The CIA is reporting that computer hackers have shut down the power grids of several large foreign cities, showing the vulnerability of infrastructure to the hackers:

Hackers literally turned out the lights in multiple cities after breaking into electrical utilities and demanding extortion payments before disrupting the power, a senior CIA analyst told utility engineers at a trade conference.

All the break-ins occurred outside the United States, said senior CIA analyst Tom Donahue. The U.S. government believes some of the hackers had inside knowledge to cause the outages. Donahue did not specify what countries were affected, when the outages occurred or how long the outages lasted.

He said they happened in "several regions outside the United States." "In at least one case, the disruption caused a power outage affecting multiple cities," Donahue said in a statement.

"We do not know who executed these attacks or why, but all involved intrusions through the Internet." A CIA spokesman Friday declined to provide additional details.