A system engineer who worked at a contractor for an affiliate of Benesse Holdings Inc. late last year has admitted to involvement in a massive leak of Benesse customer data, sources close to the police investigation said Monday.
The temporary employee worked at the contractor to which the affiliate, Synform Co., outsourced database management services for Benesse, the biggest provider of correspondence education for children in Japan.
Benesse said it has so far confirmed that the leaked data covered 7.6 million customers but the actual number may be as high as 20.7 million.
The leak occurred at a Synform office in Tokyo late last year when the temporary worker's ID was used to access the data, the sources said.
The data are believed to have been copied to USB memory and sold to software developer Justsystems Corp. via multiple name-list traders, they said.
The leak came to light after Justsystems used the Benesse customer data purchased in May to send out direct mail the following month.