There are also serious concerns about North Korea's cyberwarfare capabilities, but the USA has been carrying out operations of its own to counter North Korean cyber operations in Northeast Asia and elsewhere.
Two supersonic US bombers flew over the Korean Peninsula in their first nighttime training mission with South Korean forces, a clear warning to North Korea as tensions spike over its nuclear weapons program. 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. She described herself as a moderate Republican but voiced anxiety about how North Korea might respond to Trump's tough talk and tweets.
Hi comments came as North Korea's foreign minister said the U.S. president had "lit the wick of war" with North Korea and his country would be made to pay with "a hail of fire". North Korea's possession of secret war plans would require a major overhaul of how South Korea and its ally Washington would respond if there's another war on the Korean Peninsula.
Australia's foreign and defense ministers visited the heavily fortified inter-Korean border Thursday and emphasized the need to inflict "maximum diplomatic pressure" to rein in North Korea's nuclear ambition.
North Korea has test-fired several missiles and conducted what it said was a test explosion of a hydrogen bomb as it advances toward its goal of developing a nuclear-tipped missile capable of hitting the USA mainland.
The plan included instructions on how to remove leader Kim Jong-un in the case of war. -South Korean military plans from the country's defense data system a year ago. Defense officials refused to comment Wednesday.
After entering South Korean airspace, 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, the release said.
In late September, B-1 bombers flew the first mission this century north of the demilitarized zone (DMZ) that divides North Korea and South Korea.
Any trip by South Koreans to North Korea requires the Seoul government's approval, as well as the North's consent.
During Tuesday's drills, the US bombers, which flew from the Andersen Air Force Base in Guam, staged simulated air-to-ground missile striking drills off the peninsula's east coast before flying across the country accompanied by the two South Korean fighters.
It would also be the first such a meeting between the two allies since South Korean President Moon Jae-in took office in May.
The drills were conducted not long after Lee broke the news about the alleged cyberattacks to reporters.
Trump and North Korean leader Kim Jong-un exchanged heated rhetoric in recent weeks.
Separately, the Navy said a USA submarine that is capable of firing Tomahawk cruise missiles and torpedoes made a port call Saturday at the US base in the South Korean city of Chinhae.
United States operations out of Guam are particularly provocative, as most suggestions are that a real USA attack on North Korea would come from warplanes out of Guam.
Rhee said the hackers stole 235 gigabytes of data, almost 80 percent of which hasn't been identified yet.
United States defense officials have told CNN that the aircraft carrier USS Ronald Reagan will conduct scheduled exercises with the South Korean navy off the peninsula at the end of this month.