Zaif reported that attackers gained unauthorized external access to servers managing hot wallets used for cryptocurrency deposits and withdrawals between about 17:00 and 19:00 on September 14, 2018. The exchange said BTC, MONA, and BCH were transferred out without authorization, causing an estimated loss of roughly 6.7 billion yen, including about 4.5 billion yen in customer assets. Zaif withheld the specific intrusion method because the case had been reported to investigative authorities and disclosure could aid similar crimes. The company suspended affected deposit and withdrawal services, rebuilt systems, strengthened security with third-party support, and arranged financial assistance intended to protect customer assets.