File photo: Preet Bharara, US Attorney for the Southern District of New York, discusses arrests in the malware BlackShades Remote Access Too, during a news conferencel in New York.

New York - A Swedish man who US authorities say helped create malicious software used to infect half a million computers pleaded not guilty in New York on Thursday to computer hacking charges.

Alex Yucel, 24, owned and operated an organisation called BlackShades, which sold software that allowed hackers to control other people's computers remotely, recording keystrokes, stealing passwords and gaining access to personal files, according to federal authorities.

Yucel was arrested in November, as part of a global crackdown on the malicious software. He was extradited to the United States by authorities in Moldova.

During Thursday's hearing in Manhattan federal court, Yucel, wearing blue, wrinkled jail scrubs and appearing dishevelled, told US District Judge Kevin Castel that he pleaded not guilty to charges that included conspiring to commit access device fraud and access to device fraud.

Prosecutor Sarah Lai told Castel the evidence against Yucel was voluminous, including several laptop computers, tablets, e-mail accounts and BlackShades subscriber records.

Yucel faces up to 15 years in prison if convicted.

On May 19, US and European authorities announced the arrest of about 100 people as part of the crackdown on BlackShades, which has sold the software to thousands of people in more than 100 countries since 2010, according to US prosecutors.

Nineteen different countries were involved in the investigation, an FBI spokeswoman said after the arrests were made public.

In some cases, users employed the inexpensive software, known as BlackShades' Remote Access Tool (RAT), to take over computer cameras to spy on their owners, according to US officials. In other cases, officials said, users sent a ransom note, requiring payment before unlocking their victims' documents.

Yucel ran BlackShades as a business, paying a marketing director, a website developer and a team of customer service representatives, according to court documents. BlackShades generated more than $350 000 in sales between September 2010 and April 2014, the documents said.

Yucel's lawyer, Steven Glaser, declined to comment after the hearing. - Reuters