Four Ways to Check for Your Own Personal Data Breach and What to Watch For

Background: Personal data breaches have remained at high levels in recent years; the Personal Information Protection Commission reported 19,417 leak-related reports for FY2025. Tokyo Shoko Research’s tally found 180 incidents disclosed in 2025, affecting 30.63 million people, with the most common cause being "virus infection / unauthorized access." Because some cases cannot be prevented by user vigilance alone, cultivating the habit of checking yourself is important.

Limits of checking: The article clearly states there is no way to prove definitively that data has not been leaked. What can be checked is whether your information is included in already disclosed incidents or in breaches that have already been discovered; leaks that have not yet been detected cannot be found. In particular, addresses and phone numbers are mainly revealed through company notifications or public disclosures, so the article recommends combining multiple methods instead of relying on a single one.

Practical steps: Specifically, it lists four methods: (1) check notifications from companies and their websites (if you receive a notice, verify it on the official site rather than clicking links), (2) search your email address on Have I Been Pwned (HIBP), which at the time of writing holds records for 1,042 sites and about 17.8 billion accounts, (3) use Google’s and Apple’s password-check features to compare saved passwords against known breaches, and (4) look for signs of misuse by reviewing credit card statements, login histories, and disclosures of credit information (such as from CIC).

Response and precautions: If a leak is confirmed, the article explains step-by-step responses: change passwords for the affected services, stop reusing passwords, enable two-factor authentication, and contact the card issuer if a card was leaked. It also warns about scams that pretend to be "leak checks" (fake emails, paid deletion services, support scams) and emphasizes not entering passwords or card numbers on alleged leak-check pages.

Support contacts: For technical consultation or to report damage, the article lists IPA’s consultation desk, the National Police Agency’s cyber consultation desk, and the consumer hotline (188). It recommends regular checks and practical measures such as using a password manager.