Some of the stolen material, including financial and IT records, has already appeared on the darknet.
The K Club resort was hit by a ransomware attack just days before hosting the Irish Open.
Hackers allegedly gained access through the resort’s virtual private network and stole large volumes of data before encrypting files.
Some of the stolen material, including financial and IT records, has already appeared on the darknet.
The group, calling itself SafePay, left a ransom note on the club’s systems, according to The Sunday Times.
It typically demands payments in bitcoin, often amounting to 1–3 per cent of a company’s annual turnover.
The K Club confirmed a “cyber incident” but said no guest information was compromised.
It has notified the Data Protection Commission and introduced additional security measures.
Cybersecurity specialists believe the attackers are likely to be Russian-based.
Gardaí are aware of the incident.
The resort declined to say whether a ransom was paid.

Kildare Among Worst Affected Counties As 54,000 Lose Power Nationwide
Majority Of Councillors Vote To Suspend Pay Parking In Naas During Christmas Period
Children's Minister Announces Reforms Of Assessment Of Need Process, Admits System Is Broken
Council Refers Kilcock–Maynooth Shuttle Bus Suggestion To NTA For Consideration
Almost 2,000 Residents In Athy Currently Affected By Power Outages
Ireland Secures Extension Of Nitrates Derogation To 2028, Minister Heydon Confirms
Watch: Backlash As Government Video Advises Young Adults How To Cope If They Move Back Home
Dozens Of Dumping Fines And Repeat Offenders Caught In Athy CCTV Pilot At Recycling Bank