San Francisco’s Cal Club purportedly hacked by Qilin ransomware

Cybernews reports that the California Golf Club of San Francisco, an elite golf club catering to Silicon Valley executives and other high-profile clients, had 10 GB of member data allegedly stolen by the Qilin ransomware group. Nearly 12,000 files were included in the data trove obtained from Cal Club, with Qilin publishing almost two dozen files with members' personal and financial information. Analysis conducted by Cybernews researchers revealed the exposure of documents from December 2016 to September 2025 containing members' names, birthdates, gender, phone numbers, home and email addresses, membership statuses, and dues paid. Qilin's leak also shed light on the number of Cal Club's members, which has not been previously disclosed by the golf club, as well as its employees' performance evaluations, 401K details, and salary information. Such a development comes as Qilin, which has become the most prolific ransomware operation over the past year, admitted to having compromised leading Japanese beer producer Asahi Group Holdings.