Does STIR/SHAKEN Stop Spam Labels? What Call Centers Should Know

By Connectivity King

Here's the short answer: no. STIR/SHAKEN proves who is calling, or more precisely, it lets the originating provider vouch for the caller's right to use a number. It doesn't decide whether a call is wanted. Spam labels like "Spam Risk" or "Scam Likely" come from carrier analytics, and those systems look at much more than a signature.

STIR/SHAKEN still matters: good attestation gives analytics engines one more reason to trust you. But if someone tells you "just get A-attestation," they're giving you half the story. Here's the whole one, from the King's court to yours.

What STIR/SHAKEN Actually Is

STIR (Secure Telephone Identity Revisited) is a set of IETF standards. SHAKEN (Signature-based Handling of Asserted information using toKENs) is the industry framework, developed by ATIS and the SIP Forum, for deploying those standards on carrier networks.

In practice, it works like this:

Your call reaches the originating provider (the carrier that puts your call onto the IP voice network).
That provider creates a signed token, called a PASSporT, that contains the calling number, the called number, a timestamp and an attestation level, and attaches it to the SIP Identity header.
The token is signed with a certificate issued under the STIR/SHAKEN governance system.
The terminating provider checks the signature and the certificate, then uses the result in its call handling and analytics.

The FCC has required voice service providers to implement STIR/SHAKEN in the IP portions of their networks since 2021, with later deadlines for smaller providers and extra obligations for intermediate and gateway providers.

The Three Attestation Levels: A, B and C

The attestation level is the originating provider's statement about what it knows about the caller and the number.

Level	Name	What the provider is asserting
A	Full	It originated the call, it has a direct authenticated relationship with the customer and can identify them, and it has verified that the customer has the right to use the calling number.
B	Partial	It originated the call and knows the customer, but it hasn't verified the customer's right to use that specific number.
C	Gateway	It's the entry point for a call that came from somewhere else (often an international gateway) and has no relationship with the person who started the call.

A few points matter for call centers:

A-level is about the number, not the message. It says the caller is authorized to use the caller ID. It says nothing about consent, content or whether the person on the other end wants the call.
B or C doesn't mean spoofed. It means the signer couldn't vouch for everything. Still, lower attestation can weigh against you in analytics.
Caller IDs you can't verify will often get B. If you send numbers your provider can't link to you, expect partial attestation.
Regulators are watching attestation quality. The FCC has acted against improper A-level signing and has proposed tighter attestation rules, so expect providers to verify more, not less.

What STIR/SHAKEN Does Do

Fights spoofing. It's much harder to impersonate a number when the terminating carrier can check whether the call was signed by a provider vouching for it.
Supports traceback. Signed calls make it easier to trace illegal robocalls back to their source.
Feeds analytics. Terminating carriers and their analytics partners can use attestation as one input when deciding how to treat a call.
Can enable a "verified" indicator. Some carriers and handsets show a checkmark or "Verified" for calls that pass verification, but that varies by carrier and device.

What STIR/SHAKEN Doesn't Do

It doesn't guarantee your calls won't be labeled spam. Analytics engines can and do label A-attested calls based on how the number behaves.
It doesn't check consent. A perfectly signed call to someone who never agreed to hear from you is still a compliance problem.
It doesn't always survive the whole path. The signature travels in SIP. Where a call crosses older non-IP (TDM) network segments, it can be lost unless a non-IP authentication solution is in place.
It doesn't show your name. Attestation isn't caller name (CNAM) or branded calling. Those are separate systems.
It doesn't fix reputation. If a number has gathered complaints, a signature won't erase them.

Where Spam Labels Actually Come From

On the major US wireless carriers, labels are driven by call analytics providers that look at many signals. Each uses its own models, but common factors include:

Calling patterns: volume, how fast calls are placed, how many unique numbers are dialed, call duration and answer rates.
Consumer feedback: complaints, spam reports and how people react to the calls.
Caller identity: whether the number is known to belong to a legitimate, registered business.
Authentication: attestation level and verification results.

In other words, behavior matters most. A number that dials thousands of people who didn't expect the call, hangs up on them or gets reported will pick up labels no matter how it's signed.

Verizon, AT&T and T-Mobile: Carrier-Specific Spam Labels

Each major US wireless network labels suspected spam its own way, using its own analytics partner. A clean record on one network doesn’t guarantee a clean record on the others, so check all three.

Verizon (analytics by TNS) uses labels such as “Potential Spam,” “Potential Fraud,” “Robo caller” and “SPAM?”. If you think a number is mislabeled, you can submit it through Verizon’s voice spam feedback form (voicespamfeedback.com).
AT&T (analytics by Hiya) shows labels such as “Spam Risk” or “Fraud Risk.” Businesses can request a review at att.com/reviewmycalllabel.
T-Mobile (analytics by First Orion) shows “Scam Likely” on suspected scam calls. Mislabeled numbers can be reported at callreporting.t-mobile.com.

A review request is just that: a request. None of the carriers promises to change a label, and a label can come back if the calling behavior that triggered it continues. STIR/SHAKEN helps authenticate your calls, but it isn’t a label fix on any network. What carries the most weight is calling people who agreed to hear from you, scrubbing against the National Do Not Call Registry and your internal DNC list, and keeping your numbers registered and consistent.

The Free Caller Registry

The Free Caller Registry (>freecallerregistry.com) is a free, centralized registration site run by the three call analytics providers that support the major US carriers: First Orion, Hiya and TNS. You submit your business details and outbound numbers once, and your registration goes to all three.

New to it? Follow our step-by-step Free Caller Registry guide.

Things to know:

It's free. You don't need to pay a third party just to register.
It's for US numbers. You can add numbers individually (up to 20 on the form) or upload a file for larger lists.
It's for businesses calling on their own behalf. The registry's terms say that if you're registering numbers for another business, for example as a BPO or service provider, you should contact the call protection providers directly. BPOs should coordinate with clients, who can register their own numbers.
It's not a guarantee. Registration gives analytics engines verified identity information. It doesn't promise you won't be labeled, and it doesn't replace ongoing reputation monitoring.
Expect follow-up. Each provider confirms receipt separately, and resubmitting a number doesn't help.

Reputation Hygiene That Actually Works (and Stays Legal)

The most reliable way to protect your caller IDs is to make calls people expect and to treat them well when they answer. Start with consent:

1. Get the Right Consent, and Prove It

Know which consent your calls need under the TCPA, based on the type of call (marketing or informational), the technology (live agent, autodialed, prerecorded or artificial voice) and the type of line (wireless or residential). Capture consent clearly, keep records of when, where and how it was given, and honor revocation through any reasonable method. State laws can add requirements on top of federal rules.

2. Scrub Every List

Scrub against the National Do Not Call Registry, your internal company-specific DNC list and any applicable state lists before every campaign. Use the FCC's Reassigned Numbers Database to check whether a number has been disconnected and reassigned since you got consent.

3. Respect Hours and Opt-Outs

Telemarketing calls are limited to 8am-9pm in the called party's local time under federal rules, and some states are stricter. Process opt-outs right away and push them to every system and vendor that dials for you.

4. Dial Responsibly

Keep abandoned calls within legal limits (generally no more than 3% of live-answered calls per campaign over a 30-day period under federal telemarketing rules, along with the required safe-harbor messaging), and connect answered calls to an agent promptly. Overly aggressive pacing creates hang-ups and dead air, and both hurt your reputation.

5. Use Honest, Stable Caller IDs

Send caller IDs you're authorized to use, that truthfully identify your business or your client, and that people can call back during business hours. Keep a consistent, appropriately sized set of numbers tied to real campaigns. Don't rotate or cycle numbers to dodge labels. Analytics providers watch for that pattern, it can make things worse, and it's at odds with the purpose of caller ID rules. Spoofing with intent to defraud or cause harm is illegal under the Truth in Caller ID Act.

6. Register, Monitor and Request Redress

Register eligible numbers with the Free Caller Registry, monitor how they're labeled, and if a number is mislabeled, use each analytics provider's redress process. If a number is labeled because of real complaints, fix the root cause (list source, consent, pacing, frequency or script) before you call again.

7. Identify Yourself Clearly

Agents should say who they are and why they're calling, early in the call. Clear identification reduces complaints and is required for telemarketing calls.

Where Connectivity King Fits

We handle the network side, so you can focus on running compliant campaigns. Connectivity King SIP trunks carry outbound calls over Tier-1 carrier routes, and calls that use Connectivity King DID numbers get A-level (full) STIR/SHAKEN attestation. Want to send a caller ID from another provider? Our support team confirms your authorization before we enable it. Our caller-ID reputation monitoring helps you spot labeling problems early. And if you'd like the whole stack handled for you, there's our hosted Vicidial dialer. Setting up your own Vicidial? See how to add a SIP trunk carrier in Vicidial.

This article is general information, not legal advice. Talk to your own counsel about your campaigns.

STIR/SHAKEN FAQ

Does A-level attestation prevent "Spam Likely" labels?

No. A-level attestation tells the terminating carrier that the originating provider has verified your right to use the number. Labels are based on analytics that weigh calling behavior and consumer feedback.

Why are my calls getting B attestation?

Usually because your provider hasn't verified that you're authorized to use the caller ID you're sending. Using numbers assigned to you by your provider, or completing its number verification process, typically fixes it.

Is the Free Caller Registry worth it?

For eligible US businesses calling on their own behalf, yes. It's free and gives analytics engines verified identity information. It doesn't guarantee label removal.

Can a BPO register numbers for its clients?

The Free Caller Registry is meant for businesses calling on their own behalf. BPOs registering for a client should have the client register, or contact the analytics providers directly.

Does changing numbers fix spam labels?

Not reliably, and rotating numbers to evade labels isn't a legitimate practice. Fix the cause, register eligible numbers and use the redress process.

Does STIR/SHAKEN apply outside the US?

The FCC framework covers US calls. Canada has also required STIR/SHAKEN. Other countries use their own approaches, so check the rules for each country you call.

Talk to the King About Your Caller IDs

Want carrier-grade routes with STIR/SHAKEN attestation and caller-ID reputation monitoring behind your campaigns? Request a quote. Quotes usually come back the same day. You can also email sales@connectivityking.com or call +1 (888) 885-4202, 9am Eastern to 9pm Pacific.

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