SK Telecom (SKT) detailed a KRW700 billion ($513.7 million) overhaul of its security systems on the same day Korean authorities fined it KRW30 million for negligence in a large-scale data breach in April.

The Ministry of Science and ICT penalised SKT following a joint public-private investigation and ordered the operator to conduct quarterly audits, boost internal security resources and assign direct oversight of data governance to the CEO.

SKT was found to have failed to “fulfil its duty of care” and “comply with relevant regulations”.

The operator separately acknowledged the investigation’s findings and expressed “deep regret” over the breach.

It outlined a four-pronged recovery initiative in response.

As part its Accountability and Commitment Programme, SKT pledged the major investment over the next five years to build an information protection system, double its security team and reorganise governance so the CISO reports directly to the CEO.

A further KRW10 billion fund was established to support local cybersecurity start-ups and talent development programmes across the country.

It also announced a KRW500 billion customer compensation package, which includes a cancellation fee waiver for users affected by the breach.

SKT is offering a 50 per cent discount on bills in August and 50GB of bonus data from then until end-December to its own and MVNO customers.

Enhanced membership rewards and service restoration for returning customers are also included.

SKT detailed a plan to offer free access to Zimperium’s military-grade mobile device security software to all users for one year and upped the limit on a cybersecurity compensation fund from KRW1 billion to KRW100 billion.

The package builds on SKT’s earlier efforts to implement additional security measure.

Reports indicate SKT lost more than 500,000 customers following the incident: as of late last month, it stated it completed 9 million SIM card replacements and resets.