A Turkish man has been extradited to the United States to face charges that he masterminded three cyber-attacks that caused a loss of more than $55 million to the global financial system.

Federal prosecutors in Brooklyn allege that Ercan Findikoglu hacked the computer systems of three payment processing companies to raise the limits on prepaid credit cards. Prosecutors say he then sent the stolen data to people who would go to ATMs and withdraw large sums of money before the companies discovered the intrusion.

Findikoglu pleaded not guilty Wednesday to an 18-count indictment that includes conspiracy to commit computer intrusion, bank fraud and money laundering charges.

He was arrested in Germany in 2013 and fought extradition for more than 18 months. His attorney did not immediately comment.