Iseto ransomware breach of outsourced print data
Add to my breach checkMade public · 3,076,477 people in client data
What leaked4
Hard to replace
- Income, balances, loans, credit or other financial details
- Home or delivery address
Permanent
- Health information
- Full name
- Health informationhealth-insurance generic-drug notices; 13,150 people with sensitive data · PPC
- Income, balances, loans, credit or other financial detailsdepends on the mailing: e.g. defined-contribution pension amounts, loan balances, tax amounts
To-dos
None of the harms this check covers.
What happened next14 events
Response: 11 events
Back to latest- Japan's PPC: Iseto asked its clients about secondary harm from misuse of the data and had received no such report so far
- Iseto announced that personal data of part-time staff at an Osaka site had also leaked
- VPN to be retired, authentication strengthened, client data confined to controlled areas with deletion rules and audits
- Forensic investigation complete: attackers entered through the VPN; client data had been kept on servers where it was not allowed and not deleted after the work
- Toyota City (Aichi) estimated that data of about 420,000 people may have leaked
6 more
- Tokushima Prefecture said about 200,000 records from its tax-notice printing may have leaked, data Iseto had reported as deleted
- Iseto confirmed the published data came from its servers and included personal data of clients' customers
- Possible leak of personal data held for some client organisations; those clients informed
- First notice of the ransomware attack; no leak confirmed at that point
- Servers and PCs found encrypted by ransomware; company-wide response headquarters set up
- Police informed of the attack
- Company
- Iseto
- When it happened
- Company detected it
- Made public
- Notice
- Leak confirmed
- Affected
- 3,076,477 people in client data · PPC: 2,509,886 private-sector, 566,561 public-sector; plus 441 Iseto staff
How the facts developed
- PPC guidance: 3,076,477 people, 41 direct clients, about 100 organisations including sub-contracting chains
- Iseto confirmed that data posted on the attackers' leak site on June 18, 2024 came from its servers and included clients' customer data
Sources
- Iseto company notice, (opens in a new tab)checked October 22, 2026
- Iseto company notice, (opens in a new tab)checked October 22, 2026
- 個人情報保護委員会 regulator (opens in a new tab)checked October 22, 2026
- イセトー company notice (opens in a new tab)checked October 22, 2026