The criminal syndicate had access to 500,000 Australian credit cards and approximately 30,000 credit cards have been used for fraudulent transactions amounting to more than $30 million.

The gang exploited loopholes in POS terminal security at 100 small businesses across Australia, recording card details to create counterfeit cards that were used in numerous overseas locations including Europe, Hong Kong, Australia and the United States.

Australian Federal Police (AFP) manager for cyber crime operations, commander Glen McEwen says the arrests are the result of significant cooperation across law enforcement and the financial industry.

"This is the largest data breach investigation ever undertaken by Australian law enforcement," he says. "Without the cooperation of 13 other countries, along with Australia's banking and finance sector, we would not have been able to track these illegal transactions to the criminal network in Romania. Today's successful outcome is a culmination of 17 months of hard work with these partners."

In the UK, meanwhile, another Romanian national has pleaded guilty to an ATM skimming operation that yielded the details of more than 9000 credit and debit cards. Leonid Rotaru, 32, was caught red handed as he returned to collect a card reader from an ATM he had tampered with at a branch of Sainsburys superpmarket.