SK Telecom Hacked, SIM Data Leak Raises Security Concerns
- Chaerin Lee
- 2 days ago
- 2 min read
April 26, 2025
Chaerin Lee
SK Telecom, South Korea’s largest mobile carrier with over 23 million subscribers, recently suffered a hacking incident that exposed parts of its users’ SIM data, sparking concerns over potential security risks. Although no highly sensitive personal details like resident registration numbers were leaked, the exposed SIM information includes subscriber identification numbers, which could be used in SIM swapping attacks to impersonate users and steal digital assets.
SK Telecom is currently offering a SIM protection service to prevent possible financial damage from cloned phones. However, concerns have emerged as many customers who had not subscribed to this service were left exposed to security risks. The company stated that there have been no confirmed cases of the leaked data being misused so far. On April 23 alone, over 1.01 million people newly subscribed to the protection service, bringing the total number of users to 1.61 million as of 8 a.m. on April 24.
According to SK Telecom, the first sign of suspicious internal data movement was detected at 6:09 p.m. on April 18. Later that evening, at 11:20 p.m., malicious code was identified and the cyberattack was internally confirmed. However, the incident was not reported to the Korea Internet & Security Agency (KISA) until 4:46 p.m. on April 20—approximately 45 hours after the initial detection. Under South Korea’s Information and Communications Network Act, service providers are required to report cyber breaches to the Ministry of Science and ICT or KISA within 24 hours of discovery. KISA has stated that SK Telecom violated this regulation. The company explained that the delay was due to ongoing internal investigations and that there was no intentional cover-up.
