Back to Learning CenterSecurity

What is phone number spoofing and how do you stop it?

By Samuel ChenardAugust 4, 20267 min read
What is phone number spoofing and how do you stop it?

Phone number spoofing is the practice of falsifying the caller ID transmitted with a call or text so it appears to come from a number other than the real one. Scammers use it to look like a bank, a government agency, or a local neighbour, because a familiar or trusted number is far more likely to be answered. You cannot stop others from spoofing a number outright — the caller controls what caller ID they send — but carrier-level authentication, call-blocking tools, and a few habits sharply cut how many spoofed calls reach you and how much damage they do.

At a glance

Quick takeaways

  • Spoofing fakes the caller ID, not the call itself — the displayed number is chosen by the caller.
  • Neighbour spoofing mimics your own area code and prefix so the call looks local and trustworthy.
  • Spoofing to defraud or cause harm is illegal in the US under the Truth in Caller ID Act.
  • STIR/SHAKEN is the carrier framework that signs and verifies caller ID to flag illegal spoofing.
  • You cannot prevent your number being spoofed, but you can report it, block calls, and never act on caller ID alone.
  • The same impersonation logic drives email spoofing — where DMARC, not the phone network, is the fix.

How does phone number spoofing work?

Caller ID was designed for convenience, not authentication. When a call is placed, the originating system attaches the number that should be displayed — and on many internet-based calling platforms (VoIP), that number is simply a field the caller can set. A scammer running an autodialer can put any number in that field, so the caller ID you see may have nothing to do with the line the call actually came from.

That flexibility exists for legitimate reasons. A business with dozens of outbound lines may display one main callback number; a doctor returning a call from a personal phone may show the clinic's number. The problem is that nothing in the basic caller ID system checks whether the displayed number belongs to the caller — the same gap that makes VoIP routing flexible also makes it abusable, much like the way a SIP proxy has to be secured against forged call setup.

Neighbour spoofing is the most common consumer variant: the scammer forges a number that shares your area code and first three digits, so an incoming call looks like a neighbour, a local business, or your child's school. It exploits a simple instinct — you are more likely to answer a local number than an unknown one from across the country.

Why do scammers spoof phone numbers?

The goal is almost always to get you to answer and then to trust what you hear. A spoofed caller ID is the opening move in a social-engineering script, and it works because the number does part of the persuasion before anyone speaks. Common uses:

  • Impersonating a trusted institution — a bank, the IRS, a utility, or law enforcement — to pressure you into paying or handing over credentials. This is voice phishing, or vishing, and it leans on the same playbook as other social engineering attacks.
  • Beating call screening — a local or familiar number gets past the mental filter that sends unknown numbers to voicemail.
  • Hiding the real origin — spoofing masks where the call actually came from, frustrating tracing and blocking.
  • Text-message scams — the same forging applies to SMS sender IDs, a close cousin of SMS spoofing.

Is phone number spoofing illegal?

Spoofing itself is not automatically illegal — there are legitimate uses — but spoofing with intent to defraud, cause harm, or wrongfully obtain something of value is. In the United States, the Truth in Caller ID Act prohibits that malicious use, and the TRACED Act of 2019 expanded the FCC's authority to pursue offenders and pushed carriers toward mandatory caller ID authentication. So a business displaying its main number is fine; a scammer forging your bank's number to steal from you is a federal violation.

What is STIR/SHAKEN and does it stop spoofing?

STIR/SHAKEN is the industry framework that fights spoofing at the network level. It lets a caller's phone company cryptographically sign the caller ID as it originates a call, and the receiving company verify that signature — confirming the displayed number really was authorised by the network it came from. Calls carry an attestation level indicating how confident the originating carrier is in the number.

Per the FCC's caller ID authentication program, widespread deployment reduces the effectiveness of illegal spoofing, helps carriers block bad calls before they reach you, and makes bad actors easier to trace. As of late 2023, nearly all US voice providers operating IP networks were required to have implemented it, and a December 2025 FCC review concluded the framework authenticates caller ID effectively when applied correctly.

It is not a complete cure. Calls that traverse older non-IP networks, or originate overseas beyond US rules, can still slip through unsigned. STIR/SHAKEN is why your phone increasingly labels calls "Verified" or, conversely, "Scam Likely" — but the label is a strong signal, not a guarantee.

How do you stop phone number spoofing?

You cannot prevent someone from spoofing a number, including your own, because the forging happens on the caller's side. What you can do is reduce the volume that reaches you and refuse to act on caller ID alone:

  • Don't trust the display. Treat any unexpected call claiming to be your bank, a government agency, or a vendor as unverified. Hang up and call back on a number you look up yourself.
  • Let unknown numbers go to voicemail. Answering — or worse, pressing a button to "opt out" — confirms your line is live and invites more calls.
  • Turn on your carrier's call-blocking. Major carriers offer spam-labelling and blocking built on STIR/SHAKEN data, often free; your phone's built-in "silence unknown callers" setting helps too.
  • Register with the National Do Not Call Registry (donotcall.gov). It won't stop scammers, but it makes legitimate telemarketing calls stand out as suspicious.
  • Report spoofed and scam calls to the FTC at reportfraud.ftc.gov and to the FCC at fcc.gov/complaints. Reports feed the enforcement actions the TRACED Act enables.

What if my own number is being spoofed?

If you get a wave of callbacks or angry messages from strangers, a scammer is likely spoofing your number to call other people. You cannot stop it directly, but you can: record a brief voicemail greeting noting your number may have been spoofed, avoid answering the unknown callbacks, report the incident to the FCC and FTC, and wait it out — scammers cycle through numbers quickly and usually move on within days.

Where Palisade fits

Phone number spoofing and email spoofing are the same attack wearing different clothes: forge a trusted identity, then exploit the trust. The phone network is still catching up with STIR/SHAKEN, but email already has the answer, and Palisade deploys it for you — setting up and enforcing SPF, DKIM, and DMARC so receivers reject messages that forge your domain instead of delivering them to your customers. See how exposed your domain is to impersonation today with the Email Security Score.

Questions readers ask

Frequently asked questions

See which senders are using your domain

Start in Palisade.

Get started

Keep going with AI

Ask AI how this applies to you

Take this guide to your assistant — each question opens pre-filled, with a link back to this page so it can read the details.

  • What is phone number spoofing and how do you stop it?
  • How does this apply to my domain?
  • What should I do about it, step by step?

Share this article

Samuel Chenard

Written by

Samuel Chenard

CEO & Co-Founder, Palisade

Samuel Chenard is the CEO and co-founder of Palisade, AI-first DMARC software for IT teams and MSPs, from one domain to thousands.

More from Samuel

Related articles