What is STIR/SHAKEN?

The standard exists because caller ID was trivially forgeable. Spoofing a local number was how most scam calls got answered.

Attestation comes in levels. Full attestation means the sending carrier knows the customer and vouches for their right to that number. Lower levels mean steadily less.

Your carrier uses it to decide whether to label a call as suspected spam before it ever rings.

Say a supplier in Ohio calls your shop in Arizona. Her VoIP provider knows her and knows she owns the number, so it signs the call with the top level of attestation, labeled A. (The levels run A, B and C. B means the carrier knows the customer but can't vouch for the number, and C means it only knows where the call entered its network.)

Her provider hands the call to a wholesale carrier, which passes it on to your carrier. If every link in that chain is modern internet-based equipment, the signature arrives intact and your phone may show a checkmark. But suppose the middle carrier still routes part of the journey over older, non-internet equipment. The signature can't travel across that kind of link, so it's dropped there. Your carrier receives an unsigned call from an out-of-state number and has to guess. Its guess might be "Spam Likely" for a supplier you've worked with for years.

This usually comes up the other way around: a customer mentions that your callback was labeled as spam. It helps to know that the label doesn't come from STIR/SHAKEN alone. Carriers feed attestation into analytics systems that also weigh how many calls a number makes, how short they are, and how often people report it.

Start with your carrier. Ask what attestation level your outbound calls get, and if it isn't A, ask what they need from you to fix that. Often it's just paperwork proving the number is yours.

Look at your calling pattern next. A number that places forty short calls in an hour looks like a robocaller to an algorithm, even when it's your office manager confirming tomorrow's appointments. The major call-labeling companies also run a free shared registry where a business can list its numbers, and your carrier can point you to it. None of this is instant, so expect labels to take a few weeks to clear.

Carriers handle this upstream of GreetKeeper. It shapes what reaches your forwarded line rather than being something the assistant applies.

A low attestation on an unknown number is a reasonable signal to treat a call differently, and carrier-level blocking is where that decision is cheapest to make.

Every call that does reach the line arrives as a transcript, so you can see what the filtering let through.