What is STIR/SHAKEN?
STIR/SHAKEN is the set of caller ID authentication standards US phone carriers use to digitally sign calls and confirm the calling number has not been spoofed. The FCC required it on carriers' IP networks under the TRACED Act, with the largest carriers starting in June 2021.
The originating carrier signs each call with an attestation level. A (full) means the carrier knows the customer and that they are allowed to use the number; B (partial) means it knows the customer but not their right to the number; C (gateway) means the call entered its network from elsewhere and it cannot vouch for it. The receiving carrier checks the signature and can use the result, along with other data, when it decides how to label or block a call.
For outbound teams, the practical step is to place calls through a carrier or platform that can give your numbers A-level attestation, using numbers you own and have registered. A-level attestation does not stop a number from being labeled as spam if its calling behavior looks like spam, which is where caller ID reputation comes in.