The CIA admitted Friday that a cyberattack had caused a blackout that affected multiple cities within an unidentified foreign country.

According to InformationWeek.com [1]:

Alan Paller, director of research at the SANS Institute, said that CIA senior analyst Tom Donahue confirmed that online attackers had caused at least one blackout. The disclosure was made at a New Orleans security conference Friday attended by international government officials, engineers, and security managers from North American energy companies and utilities.

In a written statement Donahue gave to Paller, he revealed that hackers had broken into the computer systems of utilities through the Internet, which they followed with extortion demands. In one instance, Donahue wrote that hackers attacked the power equipment of one region which caused a blackout affecting multiple cities. The CIA believes the hackers "had the benefit of inside knowledge."

The SANS Institute reports [2] that Donahue said "the CIA actively and thoroughly considered the benefits and risks of making this information public, and came down on the side of disclosure."

But the specifics of the attack and which cities experienced the blackout are likely to remain a mystery, according to Paller.

Strategy Page adds [3]this news worries cyberwar experts.

[They] get nervous about this sort of thing because one could fight a war using the same weapons. Shutting down power plants, and other utilities, as well as other commercial sites, has real military value. This is what bombing campaigns have done for over seventy years, and you can, in theory, do it a lot faster via network connections.

And while everyone can agree that defenses must be built, says Strategy Page, no one knows what defenses are effective.