One of the men responsible for the Gozi trojan, described by security expert Brian Krebs as “an extremely sophisticated strain of malicious software”, has been sentenced to time served.

Kimba Wood, a district judge in New York, ruled that the 21 months Deniss Calovskis has already spent behind bars is sufficient punishment. He will now be able to return home to Latvia.

Mr. Calovskis, who was first arrested in the Eastern European country in November 2012, and extradited to the US in February 2015, helped write some of the code for the Gozi trojan, which infected over one million computers around the globe.

The 30-year-old, who had pleaded guilty, was facing a much tougher sentence. However, Ms. Wood concluded that his role in this devastating and prolonged attack, which was first discovered in 2007, was minor compared to the other main offenders.

Weighing up factors such as the fact he did not create or distribute the trojan, or benefit much by way of remuneration, the judge said that Mr. Calovskis’ “unusual individual characteristics will not … cause others to follow in his footsteps by my not giving him a longer sentence”.

The Gozi trojan was created by Nikita Kuzmin, from Russia, and was disseminated by Mihai Ionut Paunescu, from Romanian. The former is currently behind bars in the US, while the latter remains in custody in Romania.

According to the FBI, the origins of the Gozi trojan – detected by ESET as Win32/Spy.Ursnif.A – goes as far back as 2005. This was when Mr. Kuzmin first “conceived” of the idea.

Designed to be distributed in numerous ways, the trojan, once downloaded, would surreptitiously install itself on a victim’s computer. It would then capture information, including sensitive banking data.

Armed with this insight, the cybercriminals would then take money out of accounts belonging to compromised users. It is estimated that this scheme has resulted in the theft and loss of tens of millions of US dollars.