North Korea has doubled the number of professional cyber warriors over the past two years and established bases outside the country, which act as sources for cyber attacks.
It writes the South Korean news agency Yonhap based on intelligence from military sources.
North Korea cyberarmy has now reached to 5900 employees from 3,000 men two years ago.
In recent years, hackers have carried out a series of attacks against South Korean military institutions, banks, government agencies and media companies. The allegations have been made against the arch-enemy North Korea, but Pyongyang argues that Seoul will only find on in attempts to increase tension between the countries.
South Korea is working hard to tighten Internet security and has since 2010 a special cyber command that will make the country less vulnerable to attacks.