But now one high-profile defector has told the BBC that even upper estimates of the DPRK's hacking capacity under-estimate reality.
Professor Kim Heung-Kwang, who escaped North Korea in 2004 after 20 years teaching computer science at the country's Hamheung Computer Technology University, told the BBC that North Korean hackers were able to destroy power and security infrastructure, kill people and even "destroy cities".
Kim estimates that in total the country now has at least 6,000 trained hackers working for the military -- higher than prior assessments. As recently as December 2014, at the time of the infamous Sony Pictures hack attributed to North Korea by the US and others, other defectors said the secretive regime only had around 1,800 "cyber-warriors". The hackers work within the General Bureau of Reconnaissance, under "Bureau 121", where they are tasked with launching espionage and other attacks on enemies including South Korea, the US and others. "There are at least two geniuses at work. I know these men. I taught some of them. The way they use code is different but I can recognise them," Heung-Kwang told WIRED for our April cover feature -- when his own best guess placed the number of state hackers in North Korea closer to 3,000. Since 2014, his estimate has doubled.
Kim told the BBC that North Korea wanted to develop its own multipurpose virus able to target nuclear facilities and other infrastructure, similar to the Stuxnet virus which disabled elements of Iranian nuclear centrifuges prior to 2010. He said that such a virus could theoretically "destroy a city" -- though it remains a purely theoretical threat at this stage and not something which is conceptually alien to its enemies. "Although the nuclear plant was not compromised by the attack, if the computer system controlling the nuclear reactor was compromised, the consequences could be unimaginably severe and cause extensive casualties," Kim said.
North Korea has responded with typical fervour. On its state-run English language news service, it reported that concerns about its cyber-attack capability were a "false story". "The world's progressive people clearly know that the DPRK hopes for peace but the US is preparing another Korean war," the state said. Adding that the accusations made by US Secretary of State John Kerry were "base ones of the incurably mad man".
This article was originally published by WIRED UK