Great Plains Health hospital continues to work through a malicious ransomware attack that occurred early in the week.

Great Plains Health CEO Mel McNea said encrypted information entered computers and created obstacles for health system staff members to access parts of the hospital network.

McNea said in some cases, the ability to care for patients was inhibited. Between the computer hack and stormy weather, many non-emergency appointments and procedures were postponed Tuesday; however, surgeries and some imaging procedures continued as scheduled.

Ransomware is malicious software designed to deny access to computer systems. The anonymous hacker tries to extort money (ransom), in exchange for restoring the systems to normal operating conditions. There is no guarantee that the victim will recover their files if they pay the ransom.

GPH staff responded to the attack at 7 p.m. Monday evening, McNea said, working through the night to minimize the impact to local health services as much as possible.

By Wednesday, services at the hospital were “continuing as normal,” the hospital said on its Facebook page. All GPHealth clinics were open Wednesday and again on Friday morning as scheduled.

Some phone lines were disrupted in the attack. Phone calls to some clinics, particularly orthopaedics, did not ring in the office. Callers were urged to leave a voice mail if they were prompted to do so. Hospital staff checked voice mail frequently and called people back right away, the hospital said Wednesday.

“We are confident that patient information was not breached in any way,” McNea said. “We will however, do a full audit to further investigate. We are working closely with law enforcement as the investigation unfolds.”

During the first three quarters this year, 491 ransomware attacks were launched on healthcare providers, according to the anti-malware and anti-virus software provider, Emsisoft. Apparently, that was just in U.S.