> JapanHacked_
[Investigating][Severity: Moderate][Lost device]

Tokyo Waterworks Bureau: four external hard drives holding personal data lost

On October 2 the Tokyo Metropolitan Government Bureau of Waterworks found that four external hard drives kept in a locked cabinet in its office at the metropolitan government building were gone, with only their cases left. The drives held material on the land the bureau owns and personal data on 1,932 people: 1,037 contacts at companies and national and local governments, and 895 local residents and others. Most entries are names only, but they include 307 addresses, 123 phone numbers and four dates of birth. The bureau said theft could not be ruled out and planned to report it to the police; when it disclosed the loss on October 23 it had seen no misuse.

Disclosed

2026-10-23

Organizations involved

1

Leaked or at risk

1.9K

1,932

Downtime

Unknown

Timeline

  1. Detected 2026-10-02
  2. Disclosed 2026-10-23
  3. 21 days

Attack or cause

Method
[Lost device]
Impact
[Data leak]
Entry point
Unknown

Data exposed or at risk

[Name][Postal address][Phone number][Date of birth]

Organizations involved

Open in organization search

Sources

  1. [1][Official]個人情報を含む情報を記録した外付けハードディスクの紛失についてBureau of Waterworks Tokyo Metropolitan Government · 2026-10-23
  2. [2][News]東京都水道局 個人情報入りハードディスク紛失NHK · 2026-10-23
  3. [3][News]東京都水道局、外付けHDD紛失 個人情報1932人分を保存The Mainichi Shimbun · 2026-10-23
  4. [4][News]東京都水道局が個人情報保存のハードディスク紛失 1900人あまりの名前や住所などを保存TBS · 2026-10-23