US Central Intelligence Agency senior analyst Tom Donohue told a gathering of 300 US, UK, Swedish, and Dutch government officials and engineers and security managers from electric, water, oil & gas and other critical industry asset owners from all across North America, that "We have information, from multiple regions outside the United States, of cyber intrusions into utilities, followed by extortion demands."

Mr Donohoe was not explicit as to whether the extortionist cyber attackers, which had brought down the power of entire cities, were terrorists with political motives or were criminals attempting to extort financial ransom. He also did not name the regions that had suffered attacks other than to say they were outside the US.

"We suspect, but cannot confirm, that some of these attackers had the benefit of inside knowledge," said Mr Donohue.

"We have information that cyber attacks have been used to disrupt power equipment in several regions outside the United States. In at least one case, the disruption caused a power outage affecting multiple cities.  We do not know who executed these attacks or why, but all involved intrusions through the Internet."

According to Mr. Donohue, the CIA actively and thoroughly considered the benefits and risks of making this information public, and came down on the side of disclosure.

Delegates at the meeting shared information on how attackers are eluding current defenses and on promising practices for mitigating the most critical vulnerabilities. They also shared a jointly developed "SCADA and Control Systems Survival Kit."