A computer at a South Korean resettlement center was hacked after it was "infected with a malicious code," the country's Unification Ministry said.

As a result, 997 North Korean defectors had their names, birth dates and addresses have been stolen. The Ministry concluded the hack to be the first large-scale information leak involving North Korean defectors.

The North Gyeongsang resettlement center is operated by the Hana Foundation, a non-profit body set up in 2010 by the Unification Ministry to provide "protection and settlement support for North Korean defectors." It is among the 25 institutes the Ministry runs to help an estimated 32,000 defectors adjust their life in South Korea.

Among these defectors, many are considered "missing persons" by North Korea, as the North Korean government does not know the identities of all defectors. Those people who have defected to the South, may have also been declared and registered as dead by the North.

While there aren't any real issues about this hack to those defectors, analysts said that there are concerns in which the leak could endanger the defectors' family members who remain in North Korea. This can also make other defectors to feel less safe living in South Korea.

The cause was said to come from an unsuspecting staff member of the resettlement who opened a suspicious email on the said computer. This installed the malicious software, opening a backdoor for the hackers to enter the system.

In a statement, the resettlement said it offered "our sincere apology" to those affected.

"The PC had been immediately disconnected and secured," it added. "The personal information that had been leaked (which includes name and birth date) will be explained individually over phone or mail. We are operating a hotline to report issues and damages."

A North Korean defector surnamed Choi told the CNN there was concern that someone working for the organization might have "purposefully leaked it."

"Once the personal information is leaked to North Korea, those people's families back home will be registered and fall under constant surveillance. They (affected defectors) are distraught," he said.

Cyber-security experts around the world have been seeing an increased sophistication of hacking coming from the North for quite some time.

Back in September for example, U.S. prosecutors charged a North Korean man alleged to have been involved in creating the malicious software used to cripple the UK's National Health Service. The incident left NHS staff reverting to pen and paper after being locked out of their computer systems.

One of the most high profile hacks linked to North Korea in recent years targeted Sony's entertainment business in 2014, which wiped out massive amounts of data and leading to the online distribution of emails, and sensitive personal data.

North Korean state media has also often threatened to silence defectors in the South who make derogatory statements about the North's regime.

"We apologize for causing worry to many defectors with this incident," the Ministry said, adding that it would "do its best to prevent such an incident from happening again" by strengthening protection of personal information using new security protocols.

The Ministry also said that no computers at other resettlement centers across the country had been hacked.