UK cybersecurity expert pleads not guilty

A British cybersecurity researcher credited with helping curb a recent worldwide ransomware attack has pleaded not guilty to federal charges accusing him of creating malicious software to steal banking information three years ago.

Marcus Hutchins entered his plea on Monday in Wisconsin federal court, where prosecutors charged him and an unnamed co-defendant with conspiring to commit computer fraud in the state and elsewhere.

Authorities arrested the 23-year-old on August 2 at McCarran International Airport in Las Vegas, where he was going to board a flight to his home in England. He had been in Las Vegas for a cybersecurity convention.

Hutchins is free on $US30,000 ($A38 trillion) bail but with strict conditions. His bond has been modified so that he can stay in Los Angeles near his lawyer and travel anywhere in the US, but Hutchins is not allowed to leave the country.

He was also granted access to use a computer for work, a change from an earlier judge's order barring him from using any device with access to the internet. Hutchins' current work wasn't detailed at Monday's hearing. The next hearing in the case was set for October 17.

The legal troubles Hutchins faces are a dramatic turnaround from the status of cybercrime-fighting hero he enjoyed four months ago when he found a "kill switch" to slow the outbreak of the WannaCry virus. It crippled computers worldwide, encrypting files and making them inaccessible unless people paid a ransom ranging from $US300 to $US600.

Prosecutors allege that Hutchins created and distributed a malicious software called Kronos to steal banking passwords from unsuspecting computer users. In addition to computer fraud, the indictment lists five other charges, including attempting to intercept electronic communications and trying to access a computer without authorisation.

The indictment says the crimes happened between July 2014 and July 2015.