Bithumb said its abnormal-transaction monitoring detected an unauthorized withdrawal of company-owned cryptocurrency at about 22:15 on March 29, 2019. The exchange assessed the incident as insider embezzlement rather than an external hack, moved all cryptocurrency to cold wallets, and temporarily blocked deposit and withdrawal services while it checked systems. Bithumb said customer assets remained protected, requested intensive investigations by KISA, cyber police, and security firms, and coordinated with other exchanges and foundations to recover the lost cryptocurrency. The notice identifies internal staff verification as the control gap and promises stronger internal workforce screening before service resumption.