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whose-number-is-this

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Investigate a phone number — E.164 normalisation with libphonenumber, phoneinfoga scanning, carrier and line-type identification, VoIP and burner detection, messaging-app registration checks, and reverse-lookup and caller-ID sources. Use for phone OSINT and reverse phone lookup, "who owns this number", identifying a burner or VoIP number, or checking whether a number is registered on WhatsApp, Telegram or Signal. Applies to vishing and business email compromise investigation, verifying a counterparty before sending payment, recruitment and marketplace scam checks, and fraud triage. Reference at useosint.com/skills/whose-number-is-this.

skills/whose-number-is-this/SKILL.md

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Last checked
Nov 11, 2026

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62
Repository last updated
Aug 3, 2026
License
MIT

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# Whose number is this

A phone number is a strong selector: expensive to acquire, hard to change, and
used as an account-recovery anchor almost everywhere. It is also the selector
investigators get most wrong, because the metadata everyone quotes — the carrier
— is frequently stale, and because a large share of numbers now belong to
software rather than to a SIM in someone's pocket. Do not call or text the
subject; that is contact, not research.

## Step 1 — Authorized scope

Read [../../ETHICS.md](../../ETHICS.md). Write down subject, objective,
in-bounds selectors, out-of-bounds actions, and the governing jurisdiction —
which matters more here than in most skills, because reverse phone lookup is
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