North Korean hackers may have stolen secret US-South Korean war plans to kill Kim Jong Un

South Korean lawmaker Lee Cheol-hee said that North Korean hackers have stolen classified military documents, including the US and South Korea's most current war plans and plans to kill Kim Jong Un, the Financial Times reports.

Lee said that defense officials revealed to him that 235 gigabytes of data had been stolen, 80% of which has yet to be identified.

But Lee said the theft included Operational Plan 5015, the US and South Korea's current plan for war with North Korea.

The news follows a May announcement from South Korea's defense ministry saying its military network had been breached. 

“This is a total failure of management and monitoring [of classified information],” Shin Jong-woo, a researcher at the Korea Defense and Security Forum told the Financial Times of the hacks.

SEE: North Korea celebrates the 20 year anniversary of Kim Jong Il's appointment: 

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North Korea celebrates 20th anniversary of Kim Jong Il's appointment
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North Korea celebrates 20th anniversary of Kim Jong Il's appointment
North Koreans celebrate the 20th anniversary of former North Korean leader Kim Jong Il's appointment as the General Secretary of the Workers' Party of Korea in Pyongyang October 8, 2017 in this photo released by North Korea's Korean Central News Agency (KCNA) on October 9, 2017. KCNA/via REUTERS. ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THIS IMAGE. NO THIRD PARTY SALES. SOUTH KOREA OUT. TPX IMAGES OF THE DAY
Fireworks explode as North Koreans celebrate the 20th anniversary of former North Korean leader Kim Jong Il's appointment as the General Secretary of the Workers' Party of Korea in Pyongyang October 8, 2017 in this photo released by North Korea's Korean Central News Agency (KCNA) on October 9, 2017. KCNA/via REUTERS. ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THIS IMAGE. NO THIRD PARTY SALES. SOUTH KOREA OUT.
North Koreans celebrate the 20th anniversary of former North Korean leader Kim Jong Il's appointment as the General Secretary of the Workers' Party of Korea in Pyongyang October 8, 2017 in this photo released by North Korea's Korean Central News Agency (KCNA) on October 9, 2017. KCNA/via REUTERS. ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THIS IMAGE. NO THIRD PARTY SALES. SOUTH KOREA OUT.
In a photo taken on October 8, 2017 participants described as 'working people, youth, and students of Pyongyang' perform during a mass gala event marking the 20th anniversary of late North Korean leader Kim Jong Il's election as general secretary of the Workers' Party of Korea (WPK) on Kim Il-Sung square in central Pyongyang. Meanwhile North Korean leader Kim Jong-Un has promoted his sister to a senior ruling party post, state media said, and praised the country's nuclear weapons programme which has sparked international alarm. / AFP PHOTO / KIM Won-Jin (Photo credit should read KIM WON-JIN/AFP/Getty Images)
In a photo taken on October 8, 2017 participants described as 'working people, youth, and students of Pyongyang' perform during a mass gala event marking the 20th anniversary of late North Korean leader Kim Jong Il's election as general secretary of the Workers' Party of Korea (WPK) on Kim Il-Sung square in central Pyongyang. Meanwhile North Korean leader Kim Jong-Un has promoted his sister to a senior ruling party post, state media said, and praised the country's nuclear weapons programme which has sparked international alarm. / AFP PHOTO / KIM Won-Jin (Photo credit should read KIM WON-JIN/AFP/Getty Images)
In a photo taken on October 8, 2017 participants described as 'working people, youth, and students of Pyongyang' perform during a mass gala event marking the 20th anniversary of late North Korean leader Kim Jong Il's election as general secretary of the Workers' Party of Korea (WPK) on Kim Il-Sung square in central Pyongyang. Meanwhile North Korean leader Kim Jong-Un has promoted his sister to a senior ruling party post, state media said, and praised the country's nuclear weapons programme which has sparked international alarm. / AFP PHOTO / KIM Won-Jin (Photo credit should read KIM WON-JIN/AFP/Getty Images)
In a photo taken on October 8, 2017 participants described as 'working people, youth, and students of Pyongyang' perform during a mass gala event marking the 20th anniversary of late North Korean leader Kim Jong Il's election as general secretary of the Workers' Party of Korea (WPK) on Kim Il-Sung square in central Pyongyang. Meanwhile North Korean leader Kim Jong-Un has promoted his sister to a senior ruling party post, state media said, and praised the country's nuclear weapons programme which has sparked international alarm. / AFP PHOTO / KIM Won-Jin (Photo credit should read KIM WON-JIN/AFP/Getty Images)
In a photo taken on October 8, 2017 participants described as 'working people, youth, and students of Pyongyang' perform during a mass gala event marking the 20th anniversary of late North Korean leader Kim Jong Il's election as general secretary of the Workers' Party of Korea (WPK) on Kim Il-Sung square in central Pyongyang. Meanwhile North Korean leader Kim Jong-Un has promoted his sister to a senior ruling party post, state media said, and praised the country's nuclear weapons programme which has sparked international alarm. / AFP PHOTO / KIM Won-Jin (Photo credit should read KIM WON-JIN/AFP/Getty Images)
TOPSHOT - In a photo taken on October 8, 2017 participants described as 'working people, youth, and students of Pyongyang' watch fireworks as they perform during a mass gala event marking the 20th anniversary of late North Korean leader Kim Jong Il's election as general secretary of the Workers' Party of Korea (WPK) on Kim Il-Sung square in central Pyongyang. Meanwhile North Korean leader Kim Jong-Un has promoted his sister to a senior ruling party post, state media said, and praised the country's nuclear weapons programme which has sparked international alarm. / AFP PHOTO / KIM Won-Jin (Photo credit should read KIM WON-JIN/AFP/Getty Images)
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The US and North Korea have been engaged in a secretive cyber war for some time, with the US reportedly conducting a large-scale attack against Pyongyang in early October on the instruction of President Donald Trump.

Since then, Russia has provided internet infrastructure support to North Korea in a move that would diversify and strengthen Pyongyang's cyber war capabilities. 

North Korea has been found responsible for a number of high-profile attacks over the years, and is still technically at war with the US and South Korea.

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SEE ALSO: Russia just helped North Korea harden its nuclear arsenal against US cyberattacks

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