Information on the extent of personal data leaks has been made available on the official homepage of each card company for individual users to check, following a massive data breach.

Credit card users are required to go through a simple identification procedure to find out the specific personal details that have been leaked -- including bank account numbers, phone numbers, home and office addresses, and credit cards numbers.

Credit card users of KB Kookmin Card, Lotte Card and NongHyup Card flooded the call centers with requests to cancel their accounts or receive a new card amid mounting concerns over secondary damage.

When a client is confirmed to have incurred financial damage because of the leak, the responsible company will have to offer full monetary compensation. Prosecutors reported the size of the leak is estimated to reach 104 million pieces of data, even covering other credit card users, as information is shared among trading partners and affiliates.

The Cyber Terror Response Center installed an around-the-clock hotline to respond immediately to related crimes. The police are also on the lookout for new smishing (SMS phishing) scams involving imposters who claim to represent banks, card companies or financial authorities.

Customers were warned not to give personal information to unidentified callers or click on links sent in text messages or emails.

The number for KB Kookmin card is 1588-1688; Lotte Card’s is 1588-8100. NongHyup does not send out notices through phone calls or mobile text messages.

By Yoon Ha-youn, Intern reporter (yhayoun@heraldcorp.com)