Photo/Illutration This building contains the Broadlink Co. facility that is supposed to wipe data from hard disks. (Shingo Tsuru)

Eighteen hard disks once used by the Kanagawa prefectural government and still containing personal information about residents, companies and civil servants were sold online in what could be the largest-ever leak of computer data.

The used disks were supposed to have been wiped clean of data or destroyed, but they were instead put up for bidding on an Internet auction site by an employee of an outside company.

Nine of the hard disks, with a total memory storage capacity of about 27 terabytes, have been recovered. But seven others also confirmed to contain data remain unaccounted for, the prefectural government said.

Two other hard disks likely used by the Kanagawa government were also auctioned off.

The Kanagawa government rents its computers from Tokyo-based Fujitsu Leasing Co., which replaces the hard disks with new ones at regular intervals.

But the company leaves the actual destroying of data on the used hard disks to another Tokyo-based company, Broadlink Co., which recycles information equipment.

A Broadlink employee in charge of wiping the data took the hard disks off the company premises and offered them for sale on the Internet.

A man who runs an information technology company bought nine of the hard disks through the auction site.

When he checked the hard disks before use at his company, he found what appeared to be data.

The hard disks had been reformatted but that did not completely erase the data.

The IT company owner recovered the data using special software and found a large number of files containing public documents belonging to the Kanagawa prefectural government.

The data had not been encrypted when it was stored on the hard disks, making it relatively easy to retrieve the information.

The man tipped off The Asahi Shimbun about the hard disks, and reporters contacted the Kanagawa prefectural government on Nov. 27 about the possible leak of information.

The prefectural government confirmed that it had used the nine disks acquired through the Internet auction by matching their serial numbers with ones that had been replaced.

At a news conference on Dec. 6, the prefectural government said 18 of its former hard disks had been posted on Internet auction sites, including the nine that were recovered from the IT company owner.

The nine other hard disks were sold over three separate auctions to as many as three individuals. The prefecture is trying to track down the buyers.

The data contained on the nine recovered hard disks included personal information regarding tax payments by residents and companies in the prefecture, corporate documents submitted to the Kanagawa government, and work records of prefectural government employees.

An official with Fujitsu Leasing declined to comment on the matter. An executive with Broadlink acknowledged that a leak had occurred but declined to provide details.

The Broadlink employee who sold the hard disks agreed to talk with The Asahi Shimbun, but he only said he had posted the hard disks on the auction site and received cash from the sales.

The employee said he had no knowledge of what kind of data might be found on the hard disks. He also said Broadlink officials were looking into what he had done and had ordered him to not divulge details to outsiders.

The hard disks were replaced this spring by Fujitsu Leasing.

The prefectural government's contract with Fujitsu Leasing has a provision commissioning Broadlink to handle the wiping of the data on the hard disks.

Fujitsu Leasing instructed Broadlink to either completely wipe all data from the hard disks or destroy the disks before disposal.

When the Kanagawa prefectural government handed over the hard disks to Broadlink, the disks had only been reformatted and were stored at a Broadlink facility in Tokyo’s Ota Ward.

But the employee did not wipe clean or destroy the disks. Instead, he posted them on the Internet auction site.

(This article was compiled from reports by Yoshinobu Motegi and Yoichiro Kodera.)