What happened?
In April 2021, "Japan's largest e-mail friend search site" Atmeltomo suffered a data breach that was later sold on a popular hacking forum . The breach exposed 1.3M records with 580k unique email addresses along with usernames, IP addresses and unsalted MD5 password hashes.
When did it happen?
The breach date in the public record is April 16, 2021. The record was added to the catalogue on August 22, 2023 and last updated there on August 22, 2023.
What information was reported as exposed?
- Email addresses
- IP addresses
- Passwords
- Usernames
These are incident-level categories. The record does not prove that every category was exposed for every affected person.
Who may be affected?
This record may be relevant to people who had an account or other relationship with Atmeltomo or used atmeltomo.com around April 16, 2021. A catalogue entry does not establish that every customer was affected or that every listed data category applied to each person. Compare the record with an official notice addressed to you.
What should you do?
Compare the organization, dates, and information categories with any notice you received. Use contact details you independently confirm.
Change exposed or reused passwords, begin with your email account, and turn on multi-factor authentication where available.
Treat unexpected breach follow-ups with caution. Do not use links or phone numbers in a suspicious message; contact the organization directly.
Choose actions that match the information involved. If you find signs that someone is using your identity, the Federal Trade Commission provides a personal recovery plan at IdentityTheft.gov.
Sources and review information
- Have I Been Pwned breach catalogue record ↗
- Federal Trade Commission: What To Do After a Data Breach ↗
- Federal Trade Commission: Credit Freezes and Fraud Alerts ↗
Page reviewed September 14, 2026 by the Data Breach Help Editorial Team. Catalogue details reflect the provider record and may change.