Information Security 6 min read

What the LINE Data Breach Reveals About Tech‑Stack Security and Governance

In December 2023 a massive data breach exposed over 510,000 LINE users, prompting the Japanese government to order LINE and its parent NAVER to overhaul their shared technology stack, tighten authentication, and separate their cloud infrastructures to prevent future security failures.

21CTO

Mar 7, 2024

What the LINE Data Breach Reveals About Tech‑Stack Security and Governance

In December 2023, the Japanese messaging app LINE suffered a major data breach that exposed the personal data of more than 510,000 users.

The Japanese Ministry of Internal Affairs and Communications issued administrative guidelines demanding that LINE and its parent company NAVER restructure their technology stack to avoid similar incidents.

LINE, created by South‑Korean internet giant NAVER, is widely used across Asia, especially in Japan and Thailand. In 2021, LINE merged with Yahoo Japan and became partially owned by SoftBank.

The guidelines describe a deep entanglement between LINE’s and NAVER’s technical teams. NAVER’s cloud can “broadly access” LINE’s environment, allowing easy retrieval of data stored in legacy messaging systems.

Authentication services are shared via a common Active Directory that contains detailed information about former LINE employees. Some of these former employees later signed contracts with LINE, and through NAVER Cloud they accessed credentials without authorization, leading to the breach. NAVER failed to detect the intrusion, leaving LINE unaware of the risk.

The document criticises the information‑security practices and data‑governance of both companies, calling for a comprehensive review, quarterly progress reports to the ministry, and a clear separation of the two services with minimal necessary links.

Key requirements include: each service must implement its own authentication tools, discontinue the shared Active Directory, and ensure that LINE user credit information is not stored on NAVER infrastructure.

The Japanese government also urges greater attention to the impact of software vendors on information security.

After machine translation, the document repeatedly stresses that LINE needs a “thorough” transformation and questions NAVER’s reliability as a partner.

LINE has accepted the recommendations, NAVER has pledged assistance, and SoftBank has acknowledged the incident, indicating it will consider applying the guidance across its broader group, which includes Japanese telecom, Yahoo Japan, and a majority stake in UK chip designer Arm.

This situation creates a highly complex project for LINE, while NAVER Cloud customers remain concerned about remaining security gaps.

What Is a Technology Stack?

A technology stack is a set of technologies used to develop an application, including programming languages, frameworks, databases, front‑end and back‑end tools, and APIs. The choice of stack can have significant downstream effects, influencing the types of integrations a team can build and the skills a company must hire.

Investing in the right elements of a tech stack is a critical step for software and internet companies, as it provides product teams with the tools needed to build, maintain, and evolve products that meet user needs.