Telecom Voicemail Default-Password Flaw Enables LINE Account Thefts, Prompting Emergency Verification Upgrades

LINE users can receive login verification codes through telephone voicemail, but some telecom voicemail services have long retained default passwords. This can allow attackers to log in remotely, intercept verification codes and take control of accounts. The vulnerability links telecom services to LINE digital identity security, creating risks of impersonation, fraud and personal data leaks in addition to the loss of account control.

Taiwan has recently seen a series of cases in which LINE users were logged out without warning and their accounts taken over, with reports from Taiwan Mobile customers drawing particular attention. Telecom operators have urgently removed default voicemail passwords and required users to set personalized passwords. The Ministry of Digital Affairs has also instructed Chunghwa Telecom, Taiwan Mobile and Far EasTone Telecommunications to review their service mechanisms and advised users to enable two-factor authentication.