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 in 2014.

Marcus Hutchins entered the plea on Monday (14 August) during a hearing in Wisconsin federal court. He and an unnamed co-defendant face charges of conspiring to commit computer fraud in the state and elsewhere. Authorities arrested the 23-year-old man on 2 August in Las Vegas airport on his way home to Ilfracombe, England, after a cybersecurity convention.

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" that slowed the outbreak of WannaCry virus.

The virus crippled computers worldwide, encrypting files and making them inaccessible unless people paid a bitcoin ransom ranging from $300 to $600 (£230 to £460).

Prosecutors allege that before Hutchins won acclaim he 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, but the court document doesn't offer any details about the number of victims. Prosecutors have not said why the case was filed in Wisconsin. The name of Hutchins' co-defendant is redacted from the indictment.

Hutchins faces decades in prison if convicted on all the charges.