Danish payment processor company Nets has advised local banks to block up to 100,000 credit cards on suspicion their security might have been compromised by hackers, it said on Wednesday.
Nets, which was floated last month, said the breach was probably linked to transactions with a single internet retailer based abroad.
None of the cards had been tampered with yet but might be in the near future, it said, adding that credit card companies including Visa and Mastercard had opened an investigation.
“By replacing possibly compromised cards preemptively, banks and shops can save an amount in the triple digit million (Danish crowns) range, which they could suffer in losses from trades made with stolen credit card information,” Nets said.
Danish lender Jyske Bank said on Wednesday it was blocking and replacing 7,000 cards.