Mizuho Bank's latest system failure unveils control, operational risks: Moody's

Half of its ATMs in Japan shut down on 28 February despite a $3.7b system upgrade just two years ago.

Mizuho Bank’s latest ATM and online banking system nationwide failure highlights the bank’s control and operational risk issues, according to report by Moody’s Investors Service.

Local reports said that 2,956 of its 5,395 ATMS in Japan stopped functioning,and some online services stopped operating on February 28.

This marks the bank’s third nationwide system outage in the past two decades, despite Mizuho investing more than US$3.7b (JPY400b) to upgrade its core banking system. The new system started operations in 2019.

Mizuho said that the recent system outage was caused by a partial system overload that occurred after to an error when the bank’s systems were transferring 450,000 time deposit accounts data whilst 250,000 other transactions were taking place.

Japan's other two megabanks, Mitsubishi UFJ Financial Group and Sumitomo Mitsui Financial Group, have not recorded similar difficulties.

The Financial Services Agency (FSA) has reportedly ordered Mizuho to report details of the incident, whilst Mizuho said it will investigate the causes and prepare countermeasures to prevent a recurrence.

Mizuho reported two similar incidents in the past two decades. In April 2002, Mizuho experienced system trouble that led to delays in processing 2.5 million automatic debit transactions when three former banks—The Dai-ichi Kangyo Bank, The Fuji Bank and The Industrial Bank of Japan—were consolidated.

The next system trouble in March 2011 was due to the huge volume of money transfers of donations for Japan's 2011 earthquake and tsunami relief. Mizuho’s overnight batch processing on 14 March 2011 was delayed, with the number of outstanding money transfers peaking at 1.16 million on 18 March.

In both cases, Japan’s FSA issued a business improvement order to MHBK to prevent a similar problem from recurring.