Suspicions that Pyongyang may have stolen intel from South Korea will do nothing to de-escalate tensions with the United States, which are already at a 50-year high following the North's rocket tests. Such flights by the powerful aircraft based in Guam incense the North, which claims they are preparation for war; Pyongyang has threatened to send missiles into the waters around Guam.
While early 80 percent of the documents had not yet been identified, they reportedly included contingency plans for South Korean special forces and information on military facilities and power plants, it said.
While North Korea was not able to hack USA power companies, there are concerns among some of observers that the regime may attempt to damage the power grid by detonating a nuclear device at a high altitude above the US, triggering an electromagnetic pulse (EMP).
The statement by South Korea's Joint Chiefs of Staff also revealed that the two bombers carried out air-to-ground missile drills in waters off the east coast of South Korea, then flew over the South to waters between it and China to repeat the drill.
It came days after he said that diplomatic efforts with North Korea have consistently failed, adding that "only one thing will work".
"Thus far, the suspected North Korean actions are consistent with a desire to demonstrate a deterrent capability rather than a prelude to an unprovoked first-strike in cyberspace; however, North Korea linked actors are bold, have launched multiple cyber attacks created to demonstrate national strength and resolve, and have little concern for potential discovery and attribution of their operations", FireEye researchers said in a blog.
Two supersonic United States bombers have flown over the Korean peninsula in a "show of force" despite Kim Jong-Un's threats to shoot them down. (STR/AFP/Getty Images) North Korean dictator Kim Jong-Un and other communist officials at an undisclosed location in North Korea in this picture released by North Korea's official Korean Central News Agency.
These plans had likely not been classified properly but defence ministry officials told Rhee the hacked documents were not of top importance, he said.
Seoul says North Korea has repeatedly staged cyberattacks on South Korean business and government websites.
"Our country has been unsuccessfully dealing with North Korea for 25 years, giving billions of dollars & getting nothing".
The Pentagon also declined to comment specifically on reports of the potential breach, but spokesman Col. Robert Manning said on Tuesday that the U.S. is "confident in the security of our operations plans and our ability to deal with any threat from North Korea".