Mizuho Bank and Resona Bank may have been hit by what is known as a distributed denial of service, or DDoS, attack, in which perpetrators overload traffic by sending enormous amounts of data.
Mizuho Bank said Tuesday users had difficulty accessing its internet banking system at around 7 a.m. on Tuesday morning due to overloaded traffic. The system, however, was restored at around 10 a.m.
Users had difficulty accessing the bank’s internet banking system for individual customers and a business site for corporate customers.
“We apologize for causing trouble for customers,” Mizuho said in a statement.
Resona Bank, meanwhile, said a glitch occurred Saturday night that made it difficult for retail customers to connect to its online banking service. The system was restored early Monday but has been unstable again since shortly after 1 p.m. the same day.
Resona Bank is investigating the cause of the glitch.
The bank’s smartphone app was also affected. Similar problems were found at Saitama Resona Bank, Kansai Mirai Bank and Minato Bank, all part of the Resona Holdings group. No customer data leaks have been confirmed at any of the banks.
Last week, MUFG Bank and Japan Airlines were also affected by glitches apparently caused by DDoS attacks.
