Data Breach Checking: How to Know If Your Data Was Exposed

Security Education: This article describes cyber threats for defensive awareness and education purposes only. Understanding how attacks work helps organizations and individuals protect themselves. Never use this information for unauthorized access or malicious purposes.

Data breaches expose billions of records every year. The 2024 National Public Data breach leaked 2.9 billion records including Social Security numbers, names, and addresses. The 2023 MOVEit breach affected over 2,600 organizations. If you have an email address, an online account, or a Social Security number, some of your data has almost certainly been exposed in at least one breach.

How Data Breaches Happen

Breaches occur through multiple vectors. SQL injection attacks exploit vulnerabilities in web applications to extract entire databases. Credential stuffing uses leaked username/password pairs from one breach to access accounts at other services. Insider threats involve employees or contractors who steal data. Misconfigured cloud storage leaves databases publicly accessible; the Elasticsearch and S3 bucket exposure problem has leaked tens of billions of records. Supply chain attacks compromise a vendor that has access to multiple organizations’ data, as demonstrated by the MOVEit and SolarWinds incidents.

Checking If You Have Been Breached

Have I Been Pwned (HIBP) is the most trusted free service. Enter your email address at haveibeenpwned.com and it returns every known breach containing that address. As of 2025, HIBP indexes over 13 billion breached accounts from more than 780 breaches. Sign up for email notifications to be alerted automatically when your address appears in a new breach.

Password-specific checks. HIBP also offers Pwned Passwords, which lets you check if a specific password has appeared in any breach. Your password manager may integrate this automatically, flagging compromised passwords during security audits.

Google and Apple breach alerts. Google’s Password Checkup (built into Chrome and Google accounts) and Apple’s Passwords app both check saved credentials against known breaches and alert you to compromised, reused, or weak passwords.

Credit monitoring services like Experian, TransUnion, and Equifax offer free weekly credit report access. Monitoring your credit reports reveals unauthorized accounts opened in your name, which is often the first sign of identity theft following a breach that exposed Social Security numbers.

What to Do After a Breach

Change the compromised password immediately. If you reused that password anywhere else, change it at every other service as well. This is the most critical step because attackers test breached credentials across hundreds of services within hours of obtaining them.

Enable two-factor authentication on the breached account and all critical accounts if not already active. Even if your new password is compromised in a future breach, 2FA prevents unauthorized access.

Watch for targeted phishing. After major breaches, attackers craft phishing emails that reference the breach itself, claiming to offer credit monitoring, password resets, or settlement payments. Always navigate directly to official websites rather than clicking links in breach notification emails.

Freeze your credit if the breach involved Social Security numbers. A credit freeze prevents anyone from opening new accounts in your name. You can lift it temporarily when you need to apply for credit. This is free at all three bureaus.

Monitor financial statements for unauthorized transactions in the months following a breach. Set up transaction alerts with your bank and credit card companies.

Ongoing Monitoring Strategy

Do not treat breach checking as a one-time activity. Set up automatic notifications at HIBP. Enable breach alerts in your password manager. Review your credit reports quarterly. Use unique email aliases for different categories of services (financial, social, shopping) so you can immediately identify which category was breached when a notification arrives.

For guidance on responding to a compromised account, see our account recovery after a hack guide. To prevent future breaches from escalating, ensure you follow our password security best practices with unique credentials everywhere.