Dublin Midlands Hospital Group has confirmed an isolated ransomware attack at the Midlands Regional Hospital in Tullamore yesterday.
There was no impact on patient care following the attack, which affected the Laboratory Information System.
There is also no evidence of other parts of the wider health service being affected by the attack, the group said.
The hospital has been assured that there is no evidence it went any further and it is working with the HSE to restore the system.
The group said business continuity plans are in operation until the full system is restored.
The HSE have informed the Data Protection Commission as a precaution.