Tokyo police believe that the massive quantity of client data copied and leaked from Internet service provider Yahoo BB occurred in mid-December.

Police arrested three people Tuesday for allegedly trying to extort money from Softbank, and confiscated a DVD that contained customer data of subscribers who had joined Internet investor Softbank Corp.’s Yahoo BB service up to December, police sources said Thursday.

Hiroshi Mori, 67, a publisher and former head of a fringe political group; Seiji Takeoka, 55, an employee at Mori’s firm; and company executive Teruaki Yuasa, 61, were arrested on suspicion of attempting to extort several billion yen by threatening to publish data on 4.6 million Yahoo BB subscribers.

Police are trying to find out how they got ahold of the data.

Yuasa informed a Softbank client company Jan. 7 that data had been leaked and showed the data of eight customers as proof.

On Jan. 20, the trio called an executive of a Softbank affiliate and said “an acquaintance has information on several million” subscribers.

The next day, they approached the executive with a printout of 130 customers’ data and demanded an “investment” of between 2 billion yen and 3 billion yen in a fictitious joint venture as well as monthly “consultation” fees of several million yen, the sources said.

They demanded cash from a Softbank executive on Jan. 23 after presenting a DVD containing the data of 4.6 million subscribers. On Jan. 26, they repeated their demand.

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