Oleksii Lytvynenko, 43, was arrested in Ireland in 2023 and extradited to the U.S. earlier this month. He pleaded not guilty in federal court Thursday.

The Russian cybercrime group attacked more than 180 organizations before members abandoned the brand and dispersed to new ransomware groups earlier this year.

The ransomware syndicate’s internal chats exposed a wide swath of the group’s inner workings.

Electronic health records and systems used to order tests, procedures and medications remain unavailable at some affected hospitals.