SAN FRANCISCO, Aug 3 (Reuters) - A cyber security researcher widely credited with helping to neutralize the global "WannaCry" ransomware attack earlier this year has been arrested on unrelated hacking charges, according to court documents unsealed on Thursday.
Marcus Hutchins, a British-based malware researcher who gained attention for detecting a "kill switch" that effectively disabled the WannaCry worm in May, was detained by the FBI in Las Vegas on Wednesday, a U.S. Justice Department spokesman said, just days after he and tens of thousands of hackers descended on the city for the annual Black Hat and Def Con conventions.
An indictment filed in a U.S. District Court in Wisconsin accused Hutchins, also known online as "MalwareTech," of advertising, distributing and profiting from malware code known as "Kronos" that stole online banking credentials and credit card data. Hutchins' alleged activity took place between July 2014 and July 2015, according to the indictment.
Hutchins, who faces six counts related to Kronos, was indicted along with an unnamed co-defendant on July 12, but the case remained under seal until Thursday, a day after his arrest.
Kronos malware downloaded from email attachments left victims' systems vulnerable to theft of banking and credit card credentials, which could have been used to siphon money from bank accounts.
The indictment alleges that the unidentified co-defendant advertised the Kronos malware on AlphaBay, a dark web marketplace that international authorities took offline last month. Investigators said the site allowed anonymous users to facilitate global trade in drugs, firearms, hacking tools and other illicit goods.
The Justice Department said Kronos was used to steal banking systems credentials in Canada, Germany, Poland, France, the United Kingdom and other countries.
Within the cyber security community, Hutchins was heralded as a folk hero for his apparent role in stopping the WannaCry attack, which infected hundreds of thousands of computers and caused disruptions at car factories, hospitals, shops and schools in more than 150 countries.
A Justice Department official said his arrest was unrelated to WannaCry.
Reuters was unable to immediately reach Hutchins or an attorney representing him.
Andrew Mabbitt, founder of cyber firm Fidus Information Security, said on Twitter that he was working to obtain a lawyer for Hutchins because he lacked legal representation. Mabbitt did not respond to a request for further comment.
"I refuse to believe the charges against @MalwareTechBlog," Mabbitt said on Twitter.
"He spent his career stopping malware, not writing it."
Hutchins' arrest was first reported by the security website Motherboard.
(Reporting by Dustin Volz, additional reporting by Joseph Menn and Eric Auchard; editing by Steve Orlofsky and G Crosse)