STIR/SHAKEN & Call Verification, Explained

STIR/SHAKEN is the caller-ID authentication system that phone carriers in the United States and Canada use to sign calls as they move through the network. It was built to answer one question that caller ID alone could not: did this call really come from the number displayed on my screen? Understanding what the system proves — and what it does not — changes how much weight you give an incoming call.

When a call is placed, the originating carrier attaches a cryptographically signed token — an attestation — vouching for the calling number. As the call travels to your carrier, each provider can verify that signature and display the result. If someone spoofs a number by faking the caller ID, the signature is missing or does not match, and carriers can flag or block the call before it rings.

The result is visible in practice: fewer blatantly spoofed calls get through, and carriers and analytics providers can build reputation data on which networks keep sending bad calls.

The signature carries a confidence level, usually shown as A, B, or C:

• ✓Full attestation (A): the carrier knows the caller and confirms they had the right to use that phone number.
• ✓Partial attestation (B): the carrier knows the caller but cannot confirm their right to the specific number — common with some business calling systems.
• ✓Gateway attestation (C): the call reached the network from somewhere the carrier cannot verify, such as an international gateway. Many scam calls arrive this way.

A 'verified' badge on your phone generally reflects this data: the call was signed, and by which level. It tells you how the call arrived — not who the caller is.

This is the part most people get wrong, in both directions. STIR/SHAKEN proves the calling number was not spoofed in transit and that a carrier vouched for the caller's right to that number. It does not prove the caller's identity, honesty, or purpose. A scammer using a real number they legitimately control can receive full attestation. A legitimate business call routed through a foreign gateway can show low attestation.

Treat call authentication the way you treat an https padlock: it confirms the channel's plumbing, not the truth of what is said through it. The stated reason for the call, the caller's behavior, and independent verification still decide whether to trust the conversation.

Despite the framework, unwanted and illegal calls persist because of three practical gaps:

• ✓International gateways: calls entering from overseas often arrive with gateway attestation, which scammers exploit deliberately.
• ✓Partial adoption: smaller and intermediate providers have historically been slower to implement full authentication, leaving unmarked paths.
• ✓Real-number abuse: scammers increasingly call from numbers they actually control — including numbers that belong to real people — which authentication cannot flag.

This is why reputation analytics, call screening, and personal verification habits all remain necessary alongside network authentication.

FilterMyCalls reviews the network evidence for calls reaching your line — including carrier attestation data — and shows it alongside the caller's stated name and reason as one of the trust signals in the screening result. A call that arrives with full attestation and a coherent reason reads differently from a gateway call making an urgent request. Combined with checks on the screening conversation itself, network evidence turns 'a caller who says they are your bank' into 'a call that behaves like your bank's.'

The honest limit stays the same: trust signals inform your decision, caller statements remain claims, and no system catches every unwanted call. For anything involving money or sensitive information, verify through an independent channel.