SEOUL (THE KOREA HERALD/ASIA NEWS NETWORK) - South Korea's Defence Ministry on Tuesday (Dec 6) confirmed that the military's intranet had been hacked in what appears to be a North Korean attack, marking its first-ever breach.

According to the ministry, malicious code was identified in the server of the military's cyber command around Sept 23. While the military earlier said that there was little chance that its intranet had been hit - since it is not connected to the Internet - an additional investigation has found that it was also attacked.

"The military formed a cyber investigative team to look into this matter and found that some military data - including confidential information - has been leaked. It appears to be a North Korean act," the ministry said.

Officials said they believed the hackers are from Pyongyang, based on the similarity of the codes used to those previously used by North Korean hackers.

They added that the attacks originated from Shenyang, China, where many North Korean hackers are believed to be based and which was thought to be the origin of a 2014 attack on Korea Hydro & Nuclear Power Co.