What Is STIR/SHAKEN?

STIR/SHAKEN is the caller ID authentication framework U.S. phone providers use to sign and verify the caller ID on calls carried over IP networks. It helps receiving providers tell whether a call really came from the number shown. It's useful, but it's often misunderstood: it doesn't decide whether a call is labeled spam, it doesn't set the caller name people see, and it can't stop every spoofed call.

What does STIR/SHAKEN actually do?

When a call starts, the originating provider adds a digital signature saying what it knows about the caller and the number. As the call moves between networks, the receiving provider can check that signature. If it verifies, the receiving provider has more confidence the caller ID is accurate.

The FCC explains the framework and its rules in Combating Spoofed Robocalls with Caller ID Authentication.

What are A, B, and C attestation?

The signing provider includes an attestation level:

• A (full): The provider knows the customer and that the customer is authorized to use the number.
• B (partial): The provider knows the customer but can't fully confirm the number.
• C (gateway): The provider is passing along a call it received from elsewhere, often from outside the U.S., and can't vouch for the source.

VentureTel signs genuine outbound calls from our network. The attestation a recipient's provider ultimately sees can depend on how the call is routed and how each network handles it, so no provider can promise A-level results on every call to every network.

Signing vs. spam reputation vs. caller name

These are three separate systems:

• Signing (STIR/SHAKEN): Is this call really from the number shown?
• Spam reputation: Do carriers and screening apps think recipients want this call? This is based on calling activity and feedback. A fully signed call can still be labeled "Potential Spam." See My Phone Number Is Coming Up as Spam.
• Caller name (CNAM): The business name some recipients see. It's looked up separately and isn't controlled by signing or by spam reputation.

Does STIR/SHAKEN stop spoofing?

It makes spoofing harder to pass off as legitimate, but it isn't universal protection. Scammers can still display any number from networks that don't sign calls, from overseas routes, or through older non-IP connections. Those calls may show as unverified, but they can still ring through. A spoofed call never passes through your phone system, so your provider can't block it at the source.

If people say your office called them when nobody did, see Caller ID Spoofing: Someone Is Using My Business Number. For a real-world example, read our news post Someone Is Spoofing My Business Phone Number.

What should my business do?

• Use authorized business numbers for outbound calls, so genuine calls can be signed correctly.
• Keep account access secure and report unusual call activity to us promptly.
• If you see spam labels, follow the steps in our spam-label article and send us a call example.
• If you have questions about how your calls are signed, contact VentureTel support and our team can review it with you.