The investigation into the Darkode cyber crime forum spanned 20 countries and was led by the US Attorney General and the Pittsburgh branch of the FBI. Since being set up in 2007, Darkode had become a major online marketplace for cyber criminals to buy and sell hacking tools, stolen credit card numbers and other banking data as well as spamming and botnet services.

The site has been described as the biggest English-speaking hacking forum and has frequently targeted banks and other financial institutions. Its alleged founder, 27 year old Slovenian Matjaž Škorjanc, was arrested in 2010 and charged with creating the popular botnet malware Mariposa, that was responsible for infecting an estimated 10 million computers including more than 40 banks.

Meanwhile the supposed administrator of the site at the time of its takedown, 27 year old Swede Johan Anders Gudmunds, allegedly created a Zeus botnet designed to steal bank account credentials.

"Of the roughly 800 criminal Internet forums worldwide, Darkode represented one of the gravest threats to the integrity of data on computers in the United States and around the world and was the most sophisticated English-speaking forum for criminal computer hackers in the world," US Attorney David Hickton said in a statement. "Through this operation, we have dismantled a cyber hornets’ nest of criminal hackers which was believed by many, including the hackers themselves, to be impenetrable."

The investigation, dubbed Operation Shrouded Horizon, was notable for the co-operation of several countries - not only the likes of Canada, the UK and Germany but also Costa Rica, Brazil, Colombia and Macedonia.