Hackers breached servers belonging to SITA, a global information technology company. The total number of travelers impacted remains unclear but the figure is over 2.1 million, most of them being participants in Lufthansa Group s Miles & More frequent flyers and awards program, the largest in Europe. The hackers breached the reservation system of an Asian airline that is a Star Alliance member between January 21 and February 11. Singapore Airlines disclosed the breach on Thursday, explaining how data of 580,000 members of its KrisFlyer frequent flyer program has been compromised.
Source: https://www.bleepingcomputer.com/news/security/sita-data-breach-affects-millions-of-travelers-from-major-airlines/