South Korean military officers have been warned not to open suspicious emails sent to them as signs of a North Korean hacking attack have been detected, a military official here said.

North Korea, which is believed to be operating a special computer hacking military unit to collect secret information on South Korea, is suspected of sending spam emails carrying viruses to collect classified information.

The communist state appears to have a long list of officers’ names, email addresses and other basic information already, according to the official.

Pretending to be graduates of Seoul’s Korea Military Academy, North Korean hackers appear to have sent messages to more than 60 South Korean officers who graduated from the same school.

“A warning was issued by the Cyber Command last week, advising officers not to open these emails as a malicious code could be activated just by opening them or downloading attached files,” a military official in Seoul said, asking not to be named due to the sensitivity of the issue.

“We believe North Korea sent these emails to break into our military computer network,” he said.

In recent years, North Korea, which currently falls far behind South Korea in the field of information technology, has been operating a hacking unit under the direct instruction of its leader Kim Jong-il and heir apparent Kim Jong-un, according to the intelligence officials here.

Although they are not seen as a serious threat to Seoul now, experts warn the North’s cyber-terror abilities may be getting stronger at an overwhelming speed as hundreds of youngsters are trained to become computer hackers each year.

North Korea’s young computer hackers are mostly ordered to break into the computer networks operated by South Korean government agencies, military and financial institutions to retrieve information, officials say.

Pyongyang also runs about two dozen Internet websites to propagandize its iron-fisted regime.

Investigators here also concluded that last month’s massive banking system crash of the National Agricultural Cooperative Federation was caused by North Korean hackers. The North denies the accusation.

The hackers who sent spam to military officers used South Korean domain hanmail.net, the military official in Seoul said.

“We are trying to find out how much information North Korea has managed to collect via these spam mails,” he said. “We believe this has been going on for a long time, but important military data would have been inaccessible as officers cannot log on to hanmail accounts in the base.”

By Shin Hae-in(hayney@heraldcorp.com)