Yoido Full Gospel Church disclosed on Wednesday that personal data tied to 850,000 members may have been stolen in a recent cyberattack. The institution in Seoul holds recognition from Guinness as the world's largest congregation.
Investigators traced stolen data to overseas servers
An initial church review found compromised names and dates of birth. The exposed files also contained change logs for resident registration numbers, phone numbers, and addresses. South Korea's internet security agency, KISA, flagged the suspected breach on Tuesday afternoon. The church responded by blocking outside access, changing server passwords, and notifying members.
Cybersecurity researchers discovered machine written logs
Cybersecurity firm Oasis Security located the stolen data on an overseas server in September while tracing internet addresses. The same server also held attack logs and account details linked to a second Seoul institution, Sarang Church. Sarang suffered a smaller data theft involving approximately 89,000 member records and 286 employee records, including data belonging to the senior pastor. The logs indicate that the Sarang breach occurred in August, prompting that church to form an emergency task force and report the incident to authorities.
Artificial intelligence played a role in recent attacks
Oasis revealed that attack records demonstrate the activity of AI sub-agents. These helper programs are launched by an artificial intelligence model to handle separate parts of a job, accompanied by long attack reports that appear machine-written. Both churches are still investigating how the intruders gained access, and the exact role of AI remains unclear.
President Lee Jae Myung confirmed on Tuesday that artificial intelligence is believed to have been used in recent hacks targeting South Korean commercial banks. A breach at Shinhan Bank exposed names, phone numbers, annual income, and borrowing limits for about 25,000 customers. Local news reports on the incident led the financial regulator to open an emergency on-site inspection.
Yoido Full Gospel Church plans to replace its firewall and hire security firms to hunt for other network weaknesses.
