What leaked about you
Breach data answers a question nothing else answers cheaply: which services did this identity actually use. That service list is almost always worth more to an investigator than the credentials in the record — and the credentials are the part you must never touch. Using a leaked password is unauthorized access, no matter how public the dump was.
What a record actually contains, and what matters
A breach record is a row from a service's user table. Typical fields: email, username, a password hash (or plaintext, in bad cases), registration date, last login, IP address at signup, display name, date of birth, physical address, security questions, and whatever the service happened to collect.
The metadata beats the credentials, every time:
| Field | Why it matters |
|---|---|
| Which service | Membership itself. This person had an account here — a fact you can rarely establish any other way |
| Registration date | Time-anchors the identity. Sign-up clusters across services link accounts |
| Username in the record | A handle you did not have. Straight into hunt-a-handle |
| Signup or last-login IP | Coarse geolocation and, more usefully, hosting-vs-residential classification |
| Display name, DOB, address | Identity attributes to corroborate elsewhere. Never treat as authoritative |
| Password pattern | Linkage evidence, analytically. Never an input to a login form |
Field-by-field interpretation: reference/record-fields.md.
Choosing a source
| Holding | Reach for | Why |
|---|---|---|
| An email, need a service list | Have I Been Pwned | Curated, deduplicated, names the breach and its data classes. Does not return credentials |
| A password you already hold (yours, or one in scope) | HIBP Pwned Passwords range API | Tells you if the password is in circulation without disclosing it |
| Need actual field values, or to search by username, phone, IP, or name | Keyed commercial services | The only way to pivot into records rather than just detecting membership |
| A specific dump circulating now | find-leaks-in-the-wild | Paste sites, forums, and channels, before anything indexes them |
Have I Been Pwned is the default starting point. It is curated: breaches are verified before loading and data classes are labelled, so a hit means something. Free web lookup for an email; the API is keyed and permits programmatic and domain-wide checks. It deliberately does not hand you passwords.
Pwned Passwords is worth understanding properly because the design is the point. You SHA-1 the password locally, send only the first five hex characters of the hash to the range endpoint, and receive every hash suffix sharing that prefix, with occurrence counts. You match locally. The service never learns which password you asked about. This makes it safe to run against credentials you legitimately hold, and it is the correct tool for a self-audit or a client remediation exercise.
Keyed commercial services — DeHashed, IntelX, and Snusbase are the commonly used ones. What differentiates them:
- Record-level search across many selector types, returning actual field values.
This is the pivot engine: username, phone, IP, and name searches, not just email.
- Corpus breadth versus curation. Broader corpora ingest more combolists and
therefore more junk; curated ones miss things. Know which side your source sits on.
- Some index documents, pastes, darkweb pages, and leaked files rather than
parsed user tables — closer to a search engine over leaked material than to a breach database.
Access model and coverage comparison: reference/source-catalogue.md.
The rule that has no exceptions
Never use a leaked credential to authenticate to anything. Not to "confirm the account exists". Not on a test account. Not on the subject's account with a client's verbal blessing. Credential stuffing is unauthorized access under computer-misuse law in most jurisdictions, and the public availability of the password is not a defence — see ../../ETHICS.md.
The same applies to derived actions: do not attempt password resets, do not use recovered security-question answers, and do not try a recovered password on a different service to test reuse. Reuse is something you infer from data you already hold, never something you test.
The real pivot: service enumeration
Work the breach list as an account map. An email appearing in a gaming forum, a fitness app, and a regional dating service tells you three platforms to investigate, three registration dates, and often three usernames — each one a seed for hunt-a-handle. The services themselves characterise the person: professional, regional, linguistic, and interest signals that no profile page would give you.
Password patterns are linkage evidence when handled correctly. If two records under different identities carry the same distinctive password — a long, non-dictionary, clearly personal string — that is meaningful correlation, and you record it as an analytic observation with the string itself redacted or hashed in your notes. A common password (password1, a keyboard walk, a football team) links nothing; thousands of people share it. Distinctiveness is the whole signal, and the evidence is the coincidence, not the credential.
Hashes are out of scope
Records commonly contain hashes: MD5 or unsalted SHA-1 on old breaches, salted schemes and purpose-built password hashes on newer ones. You will occasionally see plaintext where a service stored it unhashed, and reversible encryption where someone chose badly.
Note the hash type — it dates the breach and characterises the service's security posture, which is genuinely useful in a due-diligence context. Then stop. Cracking a hash produces a credential you are not allowed to use, so the work has no legitimate output. The exception is a self-audit or an authorized security assessment where the password holder is your client, and even then the range API answers the question without cracking anything.
Where this goes wrong
- Combolist contamination. Most large "breaches" in circulation are
combolists: aggregations of credentials from many sources, deduplicated, reshuffled, and stripped of provenance. A hit in a combolist tells you a pair appeared somewhere, not which service it came from. That destroys the service-enumeration value, which was the point.
- Recycled and fabricated breaches. Old data gets repackaged under a new
name and sold as fresh. Some "breaches" are wholly invented, or are scrapes of public profiles marketed as a hack. Check whether the alleged source has ever acknowledged an incident, and whether the record structure matches what that service would plausibly store.
- Breach date is not leak date. Three separate dates matter: when the data
was taken, when it first circulated, and when your source ingested it. They can be years apart. "Appeared in a breach dated X" says the account existed before X, not that it was active then.
- Absence proves nothing. Not appearing in any corpus means the person's
services were not breached, or the breach was never published, or your source does not carry it.
- Scrape-vs-breach confusion. A dataset assembled by scraping public
profiles is not evidence of a compromise, and reporting it as one is a factual error that damages a report's credibility.
- Stale attribution. Email addresses and phone numbers get abandoned and
reassigned. A ten-year-old record may describe someone else entirely.
- Vendor overlap masquerading as corroboration. Two commercial services
agreeing frequently means they ingested the same dump.
Confidence grading
- Confirmed — the record appears in a curated source that verified and
attributed the breach, the field structure matches the named service, and a second selector in the record corroborates independently.
- Probable — a record in a reputable commercial corpus with clear
attribution to a named service and internally consistent fields.
- Unconfirmed — a combolist hit, an unattributed dump, or a single row with
no corroborating selector. Report the existence of the hit and say plainly that the source is unattributed.
- Rejected — the alleged source has no plausible incident, the fields do not
match what that service collects, or the data is a public scrape relabelled.
Grade the breach, not just the record. A well-attributed breach makes every row in it more credible; an anonymous compilation makes every row less so.
Worked example
Self-audit for a client using a.mercer@example.com. HIBP returns four breaches. One is a large forum breach from several years back, data classes listed as email addresses, usernames, IP addresses, and password hashes.
The username in that breach is merce_ada, which the client had forgotten using. That handle goes to hunt-a-handle and turns up two live accounts the client did not know were still public — the most valuable output of the exercise and nothing to do with credentials.
The dead end: a commercial source returns a fifth "breach" attributed to a retailer, containing a home address. The retailer has never disclosed an incident, the field layout does not resemble a retail order table, and the same address appears in two data-broker records. Assessed as scraped aggregator data relabelled as a breach. Excluded from the report with the reasoning recorded.
Remediation: passwords the client still uses are checked through the Pwned Passwords range API, so no password leaves the machine. No credential from any record is used anywhere.
Pivots
| New selector | Skill |
|---|---|
| Username recovered from a record | hunt-a-handle |
| Additional email addresses | what-an-email-reveals |
| Phone number in a record | whose-number-is-this |
| Signup IP | find-exposed-servers |
| Name, DOB, address fields | find-anyone, dig-through-data-brokers |
| Corporate domain across many records | x-ray-a-company |
| The dump itself, circulating | find-leaks-in-the-wild |
| Service list as an entity map | graph-the-network |
Legal and handling notes
Holding breach data is regulated, and more tightly than most OSINT material. Under GDPR and UK data protection law, breach records are personal data — often special-category data — and processing them needs a lawful basis, a defined retention period, and demonstrable data minimisation. Some jurisdictions treat possession of certain stolen data as an offence in itself, irrespective of how you obtained it. Several commercial services restrict their data by licence to specific purposes; read the terms before you put results in a client report.
Practically: pull the minimum fields needed for the objective, do not retain credentials at all, store case material encrypted at rest with access logged, and delete on a schedule you wrote down at the start. If you are working for a subject on their own data, that is the cleanest footing available — and it is the only footing on which testing a password is ever appropriate.
