Eric Crocker, 39, of Binghamton, New York, was among 12 people charged in July when the international hacking forum was dismantled by US authorities working with law enforcement around the world.
Crocker, who went by the online moniker "Phastman," pleaded guilty to one count of violating the CAN-SPAM Act, a federal law on violations of Internet communication, the US Attorney's Office in Pittsburgh said in a statement.
Prosecutors said Crocker used a hacking tool called Facebook Spreader to break into protected computers.
Crocker and other Darkode hackers would then sell access to affected computers to people seeking to send out commercial messages. They were periodically paid between $200 (roughly Rs. 13,000) and $300 (roughly Rs. 19,500) for every 10,000 active computer infections.
Crocker faces up to three years in prison, a fine of $250,000 (roughly Rs. 1.6 crores), or both, the statement said. Sentencing is set for November 23.
The Federal Bureau of Investigation and the US Attorney's Office in Pittsburgh led the investigation into Darkode, known as Operation Shrouded Horizon. It included authorities from Europol and 20 countries in Europe and Latin America as well as Israel, Nigeria and Australia.
Last month, the above-mentioned authorities shut down the Darkode online forum used by cybercriminals around the world and charged 12 people linked to the site. US Attorney David Hickton had announced the charges in Pittsburgh, and called Darkode "a cyber hornet's nest of criminal hackers."
Edited by NDTV staff from original copy by Reuters
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