At least seven online retailers have been hit by a scam resulting in the possible breach of some 15,000 customers' credit card data between October last year and April, according to companies operating the websites.

In the scam, personal information was stolen after customers typed in data necessary to make payments on fake settlement screens that they believed were genuine.

Among the sellers compromised was an e-book site operated by Tokyo-based DLmarket Inc., which said in December the credit card information of up to 7,741 customers had been leaked. It later stopped selling items, and in June the entire site will be temporarily closed.