STIR/SHAKEN Explained: How Telecom Attestation Reduces Robocalls

If you’ve ever received a call from your own number, a government agency you’ve never dealt with, or a business that turns out to be a scammer — you’ve experienced caller ID spoofing. STIR/SHAKEN is the technical framework designed to stop that.

For businesses making legitimate outbound calls, understanding STIR/SHAKEN isn’t just academic. Your caller reputation score determines whether your calls are labeled “Spam Likely” or answered at all.

What STIR/SHAKEN Actually Does

STIR stands for Secure Telephone Identity Revisited. SHAKEN stands for Signature-based Handling of Asserted information using toKENs. The awkward acronyms conceal a straightforward idea: digitally signing caller ID information so it can be verified end-to-end.

When a call is made, the originating carrier validates the caller’s right to use the number they’re presenting as their caller ID. They then attach a cryptographic signature to the call. When that call arrives at the terminating carrier, the signature is verified. If everything checks out, the call receives an attestation level.

The Three Attestation Levels

A — Full Attestation: The carrier knows the customer and confirms they have the right to use the presented number. This is the highest-trust level and the one that results in calls being displayed normally.

B — Partial Attestation: The carrier knows the customer but cannot confirm their right to the specific number. This might apply to a business using a number sourced from another carrier.

C — Gateway Attestation: The call arrived from outside the carrier’s network and cannot be verified. This is the lowest trust level and the most likely to be flagged by downstream carriers and call analytics apps.

Why This Matters for Your Business

If your calls are getting labeled “Spam Likely” by carriers or call-screening apps like Hiya, Nomorobo, or Google’s screening feature, low STIR/SHAKEN attestation may be a contributing factor.

The answer rates on calls labeled as spam are dramatically lower — often below 10% — compared to calls that display cleanly. For businesses doing outbound sales, collections, appointment reminders, or patient outreach, this is a material business problem.

How to Protect Your Caller Reputation

Use a reputable carrier that provides A-level attestation. If your outbound calls originate through a carrier that properly validates your ownership of your numbers and provides full attestation, you start with the highest trust level.

Register your numbers. The Free Caller Registry (freecallerregistry.com) allows businesses to submit their caller ID information directly to the major analytics providers. This helps ensure your legitimate calls are identified correctly even when users check who’s calling.

Avoid high-volume short-duration calling patterns. Robocallers make thousands of calls per hour, many of which last only seconds. If your outbound campaigns look similar — rapid successive dials, very short average call durations — carrier algorithms will notice.

Monitor your number reputation. Tools are available to check whether your business numbers have been flagged. Check periodically, and if you find flagged numbers, go through the remediation process with the relevant analytics provider.

SIPSTACK’s Role in the STIR/SHAKEN Ecosystem

SIPSTACK is an active participant in the Canadian telecom ecosystem’s STIR/SHAKEN implementation, providing A-level attestation for customers using their own verified numbers. The platform also includes anomaly detection that flags patterns consistent with fraud before they damage your account’s reputation.

For businesses doing legitimate outbound calling, proper STIR/SHAKEN implementation is the foundation of a sustainable answer rate strategy.