Data breach checker: is your domain exposed?

What the exposure report shows

The report is built from HookPhish's breach-intelligence database — the same data that powers our continuous monitoring — and summarises everything tied to the domain you enter:

• Severity — an overall rating (none, low, medium, high or critical) that weighs how many credentials are exposed, how recent they are and whether malware logs are involved.
• Compromised employees — accounts on the domain itself (name@yourcompany.com) found in breach data. These are the highest-risk records because they open the door to your internal systems.
• Compromised users — customer or member accounts that registered on your services with other email domains and appear in leaks associated with you.
• Public breaches — whether the domain appears in known, publicly disclosed breach datasets.
• Malware logs — whether credentials for the domain appear in infostealer logs, which means a device somewhere had saved passwords, cookies and sessions harvested by malware.
• Dark web mentions and last seen — how often the domain is referenced across dark web forums, markets and leak sites, and the most recent sighting.
• Malicious ASNs — the number of autonomous systems (hosting networks) with a malicious reputation seen interacting with the domain's exposed data.

Employee exposure vs. customer exposure

The two numbers call for different responses. Compromised employees mean someone can try those passwords against your Microsoft 365, Google Workspace, VPN or remote-desktop logins today. The fix is operational: reset the password, kill active sessions, enforce MFA and check the device if a malware log is involved.

Compromised users point to a customer-facing risk: account takeover, fraud and, under GDPR and similar laws, a possible notification obligation if the leak originated from your own systems. Here the priority is to confirm the source of the leak, force resets on the affected accounts, and watch for credential-stuffing spikes against your login endpoints.

Where leaked credentials come from

• Third-party breaches — a SaaS tool, forum or supplier is breached and the dump includes your staff's work email and a reused password.
• Infostealer malware — RedLine, Lumma, Vidar and similar stealers lift every saved browser password, cookie and session token from an infected laptop or home PC and upload them to a log that is sold within hours.
• Combolists — attackers merge old breaches into huge email:password lists and replay them against popular services, which is why a 2019 password can still cause a 2026 incident.
• Phishing — credentials entered on a lookalike login page are added to the same markets. Our free URL scanner helps you spot those pages before you type anything.

What to do if your domain is exposed

1. Identify the affected accounts. The free report shows counts; HookPhish monitoring shows which accounts, which breach and whether the password is in plain text.
2. Force password resets on exposed employee accounts and revoke active sessions and refresh tokens — a reset alone doesn't log out an attacker who already holds a session cookie.
3. Enforce multi-factor authentication, preferring phishing-resistant methods (passkeys or FIDO2 keys) for admins and finance roles.
4. If malware logs are present, treat the source device as compromised: isolate it, run an endpoint scan and rotate every credential that was saved in its browser.
5. Check for reuse. Ask affected staff whether the same password was used elsewhere, and block known-breached passwords at your identity provider.
6. Switch on continuous monitoring so new leaks trigger an alert within hours rather than being discovered after an incident.