Hosei University: an attack on its contractor Nippon Steel Solutions may have leaked the names and email addresses of 16,542 students and staff

1. 2025-03-07

   Nippon Steel Solutions detected suspicious access to an internal server and isolated the server from the network. [1] [2]

2. 2025-06-23

   Nippon Steel Solutions gave Hosei University its final investigation report. [2]

3. 2025-08-06

   Hosei University announced that personal data may have leaked. [1] [2] [3]

The 16,542 people are 8,363 students admitted from fiscal 2000 to 2022, 7,438 staff on the rolls from fiscal 2018 to 2022 and 741 unclassified people. Their names, email addresses, phone numbers, affiliations and integrated authentication IDs may have leaked. No highly sensitive data was included. It notified 2,892 people by email and informed the other 13,650, who could not be reached, by a notice on its website. No leak on the dark web or elsewhere has been found. [1] [2]

Nikkei xTECH reported that Nippon Steel Solutions had announced in July 2025 that a zero-day attack in March may have leaked data on its partners and others. [1]