South Korean police attributed the 2021 Seoul National University Hospital breach to a North Korean hacking organization after investigating intrusions that used seven domestic and overseas servers as attack infrastructure from around May to June. The attackers exploited a hospital server vulnerability to enter the internal network and were assessed to have exposed personal information for roughly 830,000 patients and current or former employees, with attribution based on overlaps in IP addresses, account-registration data, IP-laundering techniques, intrusion methods, and North Korean vocabulary.