A spokesperson for Aer Lingus has confirmed that around 5,000 of its employees have been affected by a cyber attack that has compromised personal information.
The airline is among a number of global companies that have notified staff about the cyber attack. Aer Lingus also said that a "significant but lesser number of former employees" have also been affected.
The incident relates to a flaw in a piece of software called MOVEit Transfer, used by thousands of companies globally to transfer files, which could be exploited by cyber criminals.
Companies using the software were urged last week to take immediate action.
The UK's leading payroll provider Zellis said that eight of its customers have been impacted by the "global issue", which may have exposed personal information, including names, addresses, and banking details.
In a statement, Aer Lingus said Zellis had informed the company that it had "experienced a cybersecurity incident, which has resulted in a disclosure of some of our current and former employee data".
"However, it has been confirmed that no financial or bank details relating to Aer Lingus current or former employees were compromised in this incident. It has also been confirmed that no phone contact details relating to Aer Lingus current or former employees were compromised.
"The third-party provider has confirmed that the incident has been contained and that they have officially notified the Data Protection Commissioner (DPC) and the National Cyber Security Centre, as has Aer Lingus."
Aer Lingus added: "All current employees have been impacted and a significant number of former employees have been impacted.
"The affected data consists of; employee number, title, name, date of birth, address line 1, email address, start date and end date of employment, and in the majority of cases, PPS/Social Security numbers."
It said it has told employees of the issue and "provided them with advice, as well as establishing a dedicated phone line, email address and additional support from our cyber security and data privacy teams".
We need your consent to load this rte-player contentWe use rte-player to manage extra content that can set cookies on your device and collect data about your activity. Please review their details and accept them to load the content.Manage Preferences
The hack has suspected links to a Russian-speaking cybercrime gang called Clop, according to a report in The Telegraph.
A MOVEit spokesperson said: "Our customers have been, and will always be, our top priority. When we discovered the vulnerability, we promptly launched an investigation, alerted MOVEit customers about the issue and provided immediate mitigation steps.
"We disabled web access to MOVEit Cloud to protect our Cloud customers, developed a security patch to address the vulnerability, made it available to our MOVEit Transfer customers, and patched and re-enabled MOVEit Cloud, all within 48 hours. We have also implemented a series of third-party validations to ensure the patch has corrected the exploit.
"We are continuing to work with industry-leading cybersecurity experts to investigate the issue and ensure we take all appropriate response measures. We have engaged with federal law enforcement and other agencies with respect to the vulnerability."
Zellis said in its own statement: "We can confirm that a small number of our customers have been impacted by this global issue and we are actively working to support them.
"Once we became aware of this incident we took immediate action, disconnecting the server that utilises MOVEit software and engaging an expert external security incident response team to assist with forensic analysis and ongoing monitoring.
"We employ robust security processes across all of our services and they all continue to run as normal."
British Airways and Boots were also affected.
A Boots spokeswoman said: "A global data vulnerability, which affected a third-party software used by one of our payroll providers, included some of our team members' personal details.
"Our provider assured us that immediate steps were taken to disable the server, and as a priority we have made our team members aware."
British Airways, which has around 34,000 people employed in the UK, also confirmed it was one of the companies to be caught up in the cyber attack.
"We have notified those colleagues whose personal information has been compromised to provide support and advice," a spokesman said.
British Airways and Zellis have both reported the incident to the Information Commissioner's Office (ICO), the firm said.
The BBC is also understood to have been affected by the incident via Zellis, according to The Telegraph.
A spokesperson for the Department of the Environment, Climate and Communications has said that the National Cyber Security Centre (NCSC) has issued a public advisory on a critical vulnerability affecting MOVEit Transfer service last week.
In a statement, the spokesperson said that the NCSC is aware that the vulnerability has been actively exploited by malicious actors.
The spokesperson said that any entity that believes it has been a victim of the hack should report the incident to the NCSC which, the spokesperson said, does not comment on operational matters.
Additional reporting PA, Helen Donohoe
