KT Corp.: SK Telecom gets over 340,000 users in Jan. amid KT fee waiver: data

SK Telecom Gains 340,000 Customers After KT’s Data Breach Fallout

In January, South Korea’s largest mobile carrier, SK Telecom, saw a surge of 342,000 new customers through mobile number portability (MNP) an 184.7% increase from December amid fallout from a major KT Corp. data breach. Industry data from the Korean Telecommunications Operators Association revealed that 221,000 of the new subscribers migrated from KT, a sharp rise from just 45,000 the previous month.

KT, the country’s second-largest carrier, had waived early termination fees for two weeks starting December 31 as part of a compensation package following a September data breach that led to unauthorized micropayments. The breach eroded customer trust, prompting a mass exodus to competitors.

Meanwhile, LG Uplus, South Korea’s third-largest operator, also benefited, gaining 183,000 MNP users a 102.3% month-over-month increase including 80,000 from KT. Despite the losses, KT’s own MNP inflows grew 53.2% to 121,000 users in January, though the net impact remained negative.

The shift underscores the financial and reputational consequences of data breaches in highly competitive markets, with customers prioritizing security in their choice of mobile providers.

Source: https://en.yna.co.kr/view/AEN20260212008000320

KT Corp. TPRM report: https://www.rankiteo.com/company/kt-corp-worldwide

"id": "kt-1771201475",
"linkid": "kt-corp-worldwide",
"type": "Breach",
"date": "9/2025",
"severity": "60",
"impact": "2",
"explanation": "Attack limited on finance or reputation"

{'affected_entities': [{'industry': 'Telecommunications',
                        'location': 'South Korea',
                        'name': 'KT Corp.',
                        'size': 'Large',
                        'type': 'Mobile Carrier'}],
 'date_detected': '2023-09',
 'description': "KT Corp., South Korea's second-largest mobile carrier, "
                'experienced a data breach in September that led to '
                'unauthorized micropayments. The breach eroded customer trust, '
                'resulting in a mass exodus of customers to competitors like '
                'SK Telecom and LG Uplus. KT waived early termination fees as '
                'part of a compensation package, but the incident caused '
                'significant financial and reputational damage.',
 'impact': {'brand_reputation_impact': 'Erosion of customer trust',
            'data_compromised': True,
            'operational_impact': 'Customer migration to competitors',
            'payment_information_risk': 'Unauthorized micropayments',
            'revenue_loss': True},
 'lessons_learned': 'Data breaches in highly competitive markets can lead to '
                    'significant customer migration and reputational damage.',
 'references': [{'source': 'Korean Telecommunications Operators Association'}],
 'response': {'remediation_measures': 'Waived early termination fees for two '
                                      'weeks starting December 31 as '
                                      'compensation'},
 'title': 'KT Corp. Data Breach and Customer Migration to Competitors',
 'type': 'Data Breach'}