Japan's major banks to use OpenAI's new model to thwart cyberattacks, Nikkei reports (updated)

Mizuho Financial

28/05/2026 17:38

Adds details from the Nikkei report in paragraph 2, background throughout

    May 28 (Reuters) - Japan's three biggest banks — MUFG Bank, Sumitomo Mitsui Banking Corp and Mizuho Bank — are expected to gain access to OpenAI's latest model to defend against cyberattacks, the Nikkei newspaper reported on Thursday.
The model, available only to trusted partners, is believed to be on a par with that of rival Anthropic's Claude Mythos, the report said. 
The banks and OpenAI did not immediately respond to Reuters' requests for comment.
Earlier this month, Reuters reported that the three banks were expected to gain access to Claude Mythos.
Around the same time, however, Japan's finance minister said the country would establish a public-private working group to address cybersecurity risks to the financial system posed by Mythos.

 (Reporting by Nichiket Sunil in Bengaluru; Editing by Vijay Kishore and Shilpi Majumdar)
 ((Nichiket.Sunil@thomsonreuters.com;))