According to published reports in the Asahi Shimbun, one of Japan's largest dailies, a trio of banks--eBank, Mizuho Bank, and Japan Net Bank-- said that illegal transfers were made to the same receiving account, making it likely the work of just one thief.
Sources told the Shimbun that "hundreds of thousands" of yen were moved from the account of an Mizuho Bank customer on July 1, and 130,000 yen ($1,170). Losses to accounts at Japan Net Bank were not disclosed, but multiple transfers were made.
In the eBank incident, the customer reported receiving e-mail in mid-June with an attached file, bank officials told the newspaper. They speculated that spyware was installed on the customer's computer; the spyware probably had a keylogger component which watched for online bank log-in passwords, then transmitted them to the thief.
By the time eBank froze the customer's account, the transfer had already taken place, the bank said.