North Korean hackers are suspected to have hacked, stolen and leaked a massive trove of military secrets belonging to rival South Korea. The stolen data, allegedly estimated to be around 235 GB, also includes secret Seoul-Washington war plans that detail procedures on how to handle an all-out war with Pyongyang and "decapitate" Kim Jong-un's leadership.

South Korea lawmaker Rhee Cheol-hee, citing reports from the defence ministry, reportedly alleged that the data stolen by Pyongyang's state-sponsored hackers, included secret war plans titled Operational Plans 5015 and 3100.

While the former involved procedures on handling an all-out war with North Korea, the latter involved Seoul's plan on how to respond to North Korea's localised provocation or commando infiltration, Yonhap reported.

Pyongyang's hackers allegedly stole the military secrets between August and September last year. Authorities are yet to identify nearly 80% of the stolen data. The hacked and leaked data also includes specific reports on key US and South Korean military personnel.

According to local reports, the hackers also accessed information about US-South Korea military drills and data on South Korean power plants and military installations.

Pyongyang has reportedly denied being involved in the cyberattack, dismissing Seoul's claims as "fabricated".

This is not the first time that South Korea has accused Pyongyang of having launched a targeted cyberattack on its organisations. Previously, North Korean hackers were suspected of having a hand in launching cyberattacks against South Korea's air force and military.

Meanwhile, South Korea has allegedly been working to boost its cyberdefence and is believed to have adopted high-tech options in responding to threats from rival North.