KT said Thursday it had confirmed possible leaks of subscriber identification data from five-thousand-561 users through illegal micro base stations.

CEO Kim Young-seop publicly apologized, vowing full compensation and technical measures to prevent further damage.

The company reported the incident to the Personal Information Protection Commission and identified leaked IMSI data, unique numbers stored on SIM cards.

Text alerts were sent to affected customers with guidance on SIM replacement and subscription to protective services.

KT said it will provide free SIM replacements, open a 24-hour hotline, and offer SIM protection at no charge.

Officials stressed they are working with regulators to determine the cause and restore trust after the unauthorized micropayment scandal.