SK Telecom faces sharp subscriber decline following massive data breach

South Korea’s largest mobile carrier, SK Telecom, is experiencing a significant exodus of subscribers following a massive data breach in April that compromised the personal information of over 20 million users. According to data released Monday by the Korea Telecommunications Operators Association, the fallout from the incident has triggered a surge in mobile number portability (MNP), with nearly 933,509 users switching mobile service providers in May alone, a 77% increase compared to March.

The MNP figures have remained under 600,000 for the past five years but spiked to 690,954 in April following the cyberattack on SK Telecom. The upward trend continued into May, reflecting growing consumer concerns over data security and trust in the carrier’s ability to safeguard personal information.

Among those departing SK Telecom, the majority switched to KT, South Korea’s second-largest carrier, which gained approximately 196,700 former SK Telecom subscribers in May. LG Uplus, the third-largest telecom operator, saw an influx of about 158,600 users from SK Telecom during the same period. Additionally, mobile virtual network operators (MVNOs) attracted 85,180 users from SK Telecom, significantly higher than the typical monthly average of around 50,000.

In contrast, the number of subscribers transferring to SK Telecom from competing carriers dropped sharply. In May, the company drew only about 10,000 new users each from KT, LG Uplus, and MVNOs. Prior to the breach, SK Telecom regularly attracted approximately 40,000 subscribers from KT and LG Uplus combined, and around 20,000 from MVNOs.

The breach has not only impacted customer loyalty but also appears to be undermining SK Telecom’s longstanding market dominance. The Ministry of Science and ICT reported that the company’s market share has been gradually declining, slipping from 40.42 percent in January to 40.26 percent in March. Analysts suggest that, given the high rate of subscriber departures, SK Telecom’s market share is likely to fall below 40 percent in the coming months.

Over the course of April and May, SK Telecom recorded a total subscriber loss of 677,491, with only 157,631 new users signing up during the same period, resulting in a net loss of over half a million customers. Despite this, the company still retained a market share of 40.25 percent as of the first quarter of 2025, according to industry data.

In an effort to mitigate the damage and retain remaining users, SK Telecom has ramped up promotional efforts, including offering increased subsidies on new mobile devices. The company has also launched a large-scale initiative to replace compromised universal subscriber identity module (USIM) cards. As of Monday, 5.75 million users had received replacement USIMs. However, out of the 9.19 million users who requested replacements, 3.44 million are still waiting due to supply shortages.