NIS detects flaws in text message encryption on KT network smartphones

This photo shows KT's logo on its office building in Seoul, Nov. 6. Yonhap

The National Intelligence Service (NIS) has detected vulnerabilities in text message encryption on smartphones using KT's network and notified both the telecom company and the government, sources said Thursday.

In a report submitted to Rep. Choi Min-hee, the NIS verified a tip that text message encryption on certain KT-powered smartphone models could be compromised, according to the sources.

The agency confirmed that the flaw made end-to-end encryption defective and potentially susceptible to data theft during transmission.

The NIS did not disclose further details, including which smartphone models were affected or whether users' private data had been compromised.

End-to-end encryption is a security communications method that ensures only the sender and recipient can read messages, as data is encrypted on the sender's device and only decrypted on the recipient's device.

This process is designed to protect data from being accessed by any third parties, including malicious actors.

Korean mobile carriers use end-to-end encryption in line with recommendations from the Korea Telecommunications Technology Association and the International Organization for Standardization.

After the NIS notified KT and the Ministry of Science and ICT of its findings, a government-led panel began investigating potential decryption vulnerabilities across KT's entire network.

The development follows revelations by the investigation panel last week that KT allegedly concealed major malware infections and failed to report security breaches that led to a large-scale hacking and data theft case last year.

The company has also faced criticism for its delayed response to a series of unauthorized mobile payment incidents.