Bangladesh, Sept. 18 -- A cybercriminal group calling itself "iamnotavillain" has demanded a ransom of 6,000 Monero-worth roughly $3 million-from Revolut, escalating a data breach that has already exposed sensitive information belonging to hundreds of customers and triggered investigations across Britain and Italy.

The group published its demand on September 16, accompanied by a countdown threatening to sell the stolen information to other criminal organizations if Revolut does not meet the ransom deadline. The use of Monero, a cryptocurrency designed to provide greater transaction privacy than Bitcoin, adds another layer of difficulty for investigators attempting to trace the money trail.

Yet the ransom demand contains an unusual elem...