North Korea hacked into more than 140,000 computers at 160 South Korean firms and government agencies, planting malicious code, stealing 40,000 defence-related documents, police said on Monday (June 13).
The incident comes under a long-term plan laying groundwork for a massive cyber attack against its rival. Some 42,000 documents were hacked, majority of them linked to defence.
North Korea had launched a hacking campaign in 2014 but South Korea was noticed in February that Kim Jong-Un's band of hackers had been infiltrating into its networks.
South Korea suspects since the hacked machines stayed dormant, North Korea wanted to launch an attack intended to cause confusion on a national scale or to continuously steal industrial and military secrets.
South Korea has been on heightened alert against cyber attacks by the North after Pyongyang conducted a nuclear test in January and a long-range rocket launch in February that led to new U.N. sanctions.
The hackers took no action after gaining control on computers and networks of some groups but popular network management software was targeted. Cops refused of naming the platform.
The IP addresses in the attacks points towards the North.
The Pyongyang has always denied of any wrongdoing on Seoul.
In 2014, North Korean hackers led a devastating campaign against Sony pictures which led to the leakage of embarrassing internal e-mails and unreleased movie clips.
Just last month, North Korea was linked to a hacking on a Bangladeshi bank which resulted in a theft of around $ 81 million.
North Korea is not the only country with state sponsored hacking. The United States has an entire entity dedicated to hacking called the United States Cyber Command.