Blueprints for the wings of F-15 fighter jets were reportedly stolen from Korea Air Lines.
North Korean hackers have reportedly obtained blueprints to a US fighter jet.
In 2014, the country surreptitiously planted malware on more than 140,000 computers across 160 South Korean firms and agencies as part of a long-tail operation, Reuters reports.
The scheme was only discovered in February, when the North stole documents from two South Korean conglomerates.
Among them were blueprints for the wings of F-15 fighter jets, which The Hill says were stolen from Korea Air Lines.
In total, North Korea nabbed more than 42,000 documents, including more than 40,000 related to defense.
According to Reuters, the stolen documents were not classified.
The Hill notes that the IP address associated with these most recent attacks matches one from 2013, when South Korean bank and broadcast computer systems were hacked, allegedly by North Korea.
North Korea has denied any wrongdoing.
In 2014, the FBI said North Korea was responsible for a hack of Sony Pictures that took the company’s systems offline and prompted the studio to delay the launch of a film critical of North Korea.
The US later hit North Korea with sanctions over the attack.