The nation’s spy agency is investigating suspicions that North Korean hackers infiltrated a developer of South Korea’s electronic document management system. 

The National Intelligence Service(NIS) said Wednesday that an investigation is underway in relation to media reports that the developer of the On-Nara system experienced a cyberattack late last year. 

The NIS reportedly suspects North Korea is responsible for the attack, in which data was stolen from the servers of the company in charge of the development and operation of the system.

The On-Nara system, established in 2005, is an integrated program used by government agencies to produce, review and approve official documents.

In May, the personal emails of high-ranking defense ministry officials and military generals were hacked, and three months later hackers attempted to attack a government agency by impersonating a KBS reporter.