The Gozi trojan was allegedly designed by a Russian coder and spread by Romanian hacker, and made the ringleaders millions.
A hacker who helped to rip off tens of millions of dollars from victims has been released from prison after less than two years.
New York district judge said that "the goal of punishment has been served already" after Deniss Calovskis, 30, spent 21 months behind bars.
The Gozi trojan was allegedly designed by a Russian coder and spread by Romanian hacker, and made the ringleaders millions of dollars.
Calovskis - known as Miami - was held for his role in writing code for phishing pages for the gang.
A million computers were infected by the trojan, including some of those located at NASA.
Infected machines would then have complex phishing pages appear which were used to drain bank accounts surreptitiously.
Calovskis said during an earlier hearing that he was short of cash at the time of the offence, adding that his father was suffering from cancer.
In court papers his lawyer wrote: "He did not create or write the Gozi virus, he did not participate in collecting data from infected computers, and he did not personally use that data to access financial institutions."
Calovskis had been a freelance programmer at the time of the offence.
The 30-year-old had faced up to 67 years in jail before entering into a plea-bargain agreement with the US government.
He is from Latvia, and is expected to return to Eastern Europe within weeks.
