The NSA reportedly tried -- but failed -- to use a Stuxnet variant against North Korea

The NSA-led U.S. effort used a version of the Stuxnet virus designed to be activated by Korean-language computer settings, but it ultimately failed to sabotage North Korea's nuclear weapons program, according to a Friday Reuters report, which attributed the information to people familiar with the campaign.

The NSA did not respond to a request for comment.

The Stuxnet attack -- widely reported to be a joint effort by the U.S. and Israel -- succeeded against Iran's nuclear program by destroying at least 1,000 uranium-enrichment centrifuges at a nuclear plant near the city of Natanz. In the case of the effort against North Korea, however, U.S. agents reportedly weren't able to access the core machines running the nation's nuclear weapons program.

North Korea is widely known for its self-imposed isolation and secrecy. Police permission is required simply to own a computer, and Internet access is strictly limited. There's also just one primary Internet link to the nation, which comes via China.

It's no secret that the United States is concerned about the nuclear programs in both Iran and North Korea, so it's no great surprise that an effort like this might have been undertaken, said Tim Erlin, director of IT risk and security strategy for Tripwire, a security company.

North Korea's reliance on a single external Internet connection is in many ways both a strength and a weakness for the nation, Erlin added.

On the one hand, it makes the country more vulnerable to both logical and physical denial-of-service attacks, as there's a single point of failure, he said.

On the other hand, "they are simply harder to attack with precision cyber-weapons," Erlin said. There's only one way in, and it's well guarded. "That isolation comes at great cost, of course, but it does provide this advantage."