Financial losses from Internet bank fraud have hit a record high 3.5 million dollars since Japan's fiscal year began in April.
The National Police Agency says the figure, confirmed at 53 financial institutions, has already surpassed the largest full year figure.
The agency says the method employed most frequently this year involves infiltrating personal computers with spyware to steal IDs and passwords unbeknown to bank account owners. Perpetrators then use the codes to transfer money to different accounts.
Sources say losses of 260,000 dollars each have been confirmed at Rakuten Bank and Sony Bank.
The agency says the technique seen often until last year was phishing, where bank users are directed to bogus sites, enabling perpetrators to obtain users' passwords.
The police suspect that organized crime groups are involved and are calling on users to be careful.