Prof Kim Heung-Kwang told the BBC that the country had around 6,000 trained military hackers and is spending ten to 20 percent of its huge military budget on cyber war projects.
Prof Kim has called for international organisations to step in to prevent North Korea launching more severe attacks before it was too late.
For 20 years Prof Kim taught computer science at Hamheung Computer Technology University, before escaping the country in 2004.
While Prof Kim did not teach hacking techniques, his former students have gone on to form North Korea’s notorious hacking unit Bureau 121 hacking unit. He said that he keeps in contact with people in North Korea.
North Korea has been harassing other countries is to demonstrate that North Korea has cyber war capacity and it is reaching a point where their cyber-attacks could have similar impacts as military attacks, killing people and destroying cities.
A Stuxnet-style attack designed to destroy a city has been prepared by North Korea and is a feasible threat,” Prof Kim said.
Prof Kim said that if North Korea continues to cause damage in this way, an organisation such as Icann should ban North Korea from the Internet.