By bizn_fun 
Major South Korean organisations have delivered harsh criticism over the latest breach.
The editorial board of local newspaper Chosun Ilbo described the incident as “preposterous” and called for strong sanctions on firms responsible for leaks of its customer data.
Another local media outlet, the Dong-A Ilbo, said the breach is “the worst personal data leak” in Korean history.
The media outlet questioned how long the incident went unnoticed, adding that it “means their internal data protection system barely mattered.”
The breach marks the latest in a series of cyber-security incidents affecting major South Korean companies this year, despite the country’s reputation for stringent data privacy rules.
SK Telecom, South Korea’s largest mobile operator, was fined nearly $100m (£76m) over a data breach involving more than 20 million subscribers.
In September, Lotte Card also said the data of nearly three million customers was leaked after a cyber-attack on the credit card firm.