Nostrum
About the organisation
nostrum.co.jp Nostrum Corporation, based in Japan, was founded in 1991 and specializes in smartphone app development, web system development, and website construction. The company is represented by Ryoichi Jono and is registered on the J-GoodTech platform as a verified Japanese technology business. One of their flagship self-developed products is a job aptitude test preparation tool — a simulation platform replicating real SPI, TG-WEB, and similar employment exam interfaces used by major Japanese companies
What the listing means
Nostrum appeared on the thegentlemen leak site on 06 May 2026. Groups publish a victim once negotiations stall or as pressure during them, so a listing usually means data was already exfiltrated — the attack itself is dated 19 April 2026, 17 days before the listing. This group has published 134 claims in the last 30 days and remains active.
Recommended actions
- Treat any unsolicited message referencing Nostrum as suspicious — leaked data gets weaponised for phishing within days.
- If you hold an account on nostrum.co.jp, change that password now, update it anywhere you reused it, and enable two-factor authentication.
- Watch for follow-on extortion: stolen data is often re-leaked or resold after the initial listing.
- A leak-site listing is a claim made by the attacker, not a confirmed breach — check the organisation's own disclosures before acting on it.
Leak-site evidence
Listing URL https://www.ransomware.live/id/Tm9zdHJ1bUB0aGVnZW50bGVtZW4=