SEOUL-- Shinhan Card Co. said Friday that it is vetting its card numbering scheme as some issued cards turned out to be vulnerable to security and unauthorized payments.

There have been reports of unauthorized payments of its gift cards on online shopping platforms, although there has not been any reported crime involving these cards so far.

Shinhan Card's serial numbering system of its cards has been reported to be a source of such unauthorized payments.

Multiple Shinhan cards, issued in a certain month, have been assigned identical 14 or 15 digits of the 16-digit serial numbers, with the same date of expiration, according to the card firm and the Financial Supervisory Service (FSS).

It means a bunch of card numbers were assigned either in a linear order or with mostly similar digits, according to the regulator.

Card number thefts usually involve computerized algorithms, but Shinhan Card's card numbering system is judged to be vulnerable to security and unauthorized uses.

Shinhan Card did not suspend the controversial cards but said it will strengthen the monitoring of such cases.

Source: Yonhap News Agency