"North Korean Internet" is practically an oxymoron. Access to the global Internet in the secretive nation is heavily restricted and available to only select government officials and other elites. The rest of the nation has access to a closed national network called the Kwangmyong, an intranet with state-approved information, if they can access to anything at all.

It's effectively one of the most aggressive online censorship regimes on the planet. And, as it turns out, it also works pretty well at fending off foreign cyberattacks, according to a recent Reuters report.

"North Korea’s hermit infrastructure creates a cyber-terrain that deters reconnaissance," an HP Security briefing from 2013 noted. (Reuters)

Five years ago, the United States tried to sabotage North Korea's nuclear weapons program with a computer virus, Reuters reported. The campaign relied on a variant of Stuxnet -- malware that disabled Iranian centrifuges, which The Washington Post and others have reported was a joint project of the United States and Israel. The idea was to use a version of the virus that would be activated when it encountered Korean-language settings, an unnamed source told Reuters.

In pictures: Kim Jong-un on tour Show all 7 1 /7 In pictures: Kim Jong-un on tour In pictures: Kim Jong-un on tour North Korea Kim Jong-un inspecting an aquarium as he visits the Songdowon International Children's Camp in Kangwon province AFP In pictures: Kim Jong-un on tour North Korea Kim Jong-un inspecting the newly built athletic field as he visits the Songdowon International Children's Camp AFP In pictures: Kim Jong-un on tour North Korea Kim Jong-un smiling broadly along with other officials during his visit to a youth camping site in Wonsan on the southeastern coast in North Korea EPA In pictures: Kim Jong-un on tour North Korea North Korean leader Kim Jong-un visits the Songdowon International Children's Camp, as its remodelling project nears completion Reuters In pictures: Kim Jong-un on tour North Korea Kim Jong Un visits a swimming pool complex at the Songdowon International Children's Camp Reuters In pictures: Kim Jong-un on tour North Korea North Korean leader Kim Jong Un stands in the August 25 Fisheries Station under KPA 313 Unit Reuters In pictures: Kim Jong-un on tour North Korea North Korean leader Kim Jong Un inspecting the Masik Pass Hotel, ski service and lodging buildings and rest areas in the skiing courses of the Masik Pass Ski Resort in Kangwon province Getty Images

But the campaign faltered -- it was "stymied," Reuters reported, by North Korea's "utter secrecy, as well as the extreme isolation of its communications systems."

It turns out barely having an Internet infrastructure is a really good way to avoid the kind of "cyber-Pearl Harbor" US officials have been warning about for years.

Investing in offensive cyber capabilities pays off for many nations. It's much cheaper than maintaining a fleet of airplanes and battle cruisers (Reuters)

This isn't exactly a new idea: "North Korea’s hermit infrastructure creates a cyber-terrain that deters reconnaissance," an HP Security briefing from 2013 noted. "Today North Korea’s air-gapped networks and prioritization of resources for military use provide both a secure and structured base of operations for cyber operations and a secure means of communications."

North Korea's government-sponsored hackers seem to have been busy, they were thought by many to be behind a string of cyberattacks against South Korea's banking institutions in recent years. (EPA)

And while North Korea's defense gets a boost from its set-up, it also appears to value having offensive cyber capabilities. The most prominent cell of the nation's cyber troops is known as "Bureau 121," a group of roughly 1,800 hackers who are hand-picked from the nation's top universities, according to a North Korean defector who spoke with Reuters last year.

Investing in offensive cyber capabilities pays off for many nations. It's much cheaper than maintaining a fleet of airplanes and battle cruisers, and it's easy to deny responsibility for any attacks the hackers carry out. Plus, attacking digital systems has an inherent advantage: Defenders must fend off every attack to win, but hackers only need to breach a system once for a campaign to be successful.