It has been reported that nearly 400,000 SK Telecom subscribers have switched to KT and LG Uplus in the month following a hacking incident announcement.
According to the mobile telecommunications industry on the 22nd, from April 22 to May 21, 395,517 subscribers left SK Telecom. Of these, 220,709 moved to KT and 174,808 to LG Uplus. In contrast, only 43,567 subscribers switched to SK Telecom, resulting in a net loss of 351,950 subscribers for the company in a month.
SK Telecom disclosed in a press release on April 22 that subscribers’ USIM information had been hacked. The company became aware of the data breach on April 19 and reported it to the Korea Internet & Security Agency (KISA) on April 20. On April 25, SK Telecom’s CEO officially admitted the hacking and apologized, announcing that free USIM replacements would be provided.
Following the widespread announcement of the hacking incident, subscriber departures surged. Daily departures, which averaged 2,000 to 4,000 before the incident’s announcement, grew to around 35,000 per day from April 28 to May 2.
Subsequently, the departure rate reduced to around 10,000 per day, yet it remained significantly higher than usual, causing continuous subscriber losses for SK Telecom. The number of subscribers who replaced their USIMs exceeded 3 million in just one month. By May 21, a total of 3.23 million USIMs had been replaced, and 170,000 had completed USIM resets. This amounts to 14% of SK Telecom’s entire subscriber base (including budget phones) having undergone USIM replacement or resetting. There are still 5.67 million pending reservations for USIM replacements.
The demand for USIM replacements surged particularly after the second announcement from the SK Telecom breach investigation team, which revealed vulnerabilities in a server integrated with the malicious code-affected unified customer authentication server from three years ago. Despite reassurances from the investigation team and SK Telecom that IMEI information was not leaked and that any possible leak would be protected by USIM protection services and abnormal authentication attempt blocking systems (FDS), consumer anxiety persisted.
Since the investigation team’s announcement, USIM replacements have reached record daily highs, with numbers increasing from an average of around 100,000 to 300,000 per day, peaking at 360,000 replacements in a single day on May 21.
Lim Bong-ho, the head of SK Telecom’s MNO business division, stated that around 2.2 million customers have not yet received guidance on USIM replacement or resetting. He anticipated that guidance would be provided to these individuals by this week or, at the latest, next week, ensuring that all pending reservations receive notifications by the end of the month.
He further explained that for those who have not completed their USIM replacements by then, communications will be reissued early next month to encourage replacements. Additionally, once the replacement situation stabilizes, SK Telecom is considering allowing walk-in USIM replacements for customers without reservations.