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Stir/Shaken

What is STIR/SHAKEN?

STIR/SHAKEN is a mechanism that allows the person receiving a phone call to judge the validity of the caller ID presented. It's part of the fight against illegal bad-guy robocalls, which rely heavily on presenting fake caller IDs, both to evade detection and in order to trick the receiving party into answering the call. As of 30th June 2021, STIR/SHAKEN is live in North America and supported by all major carriers. Further progress will see it supported by all carriers in that region and, likely, in other regions also.

How does it work?

When a call is placed, the validity of the caller ID is attested, and this attestation plus the call setup information are digitally signed. The receiving carrier can then use that digital signature to check the correctness of the information provided, and pass the caller ID attestation level to the person receiving the call. In this way, that person can judge whether the caller ID presented to them is valid.

There are three levels of attestation:

  • Level A (Full) - the provider recognizes the entire phone number as being registered with the originating subscriber.
  • Level B (Partial) - the call originated with a known customer but the entire number cannot be verified.
  • Level C (Gateway) - the call can only be verified as coming from a known gateway.

STIR/SHAKEN on Aculab Cloud

With STIR/SHAKEN attestation essentially conveying a level of trust, we in turn need to trust our customers in order to enable it. Please contact us if you'd like us to enable attestation on your account.

Once enabled, Aculab Cloud will attest the caller IDs used on outbound calls to +1 numbers as follows:

  • Caller ID is +1 and owned under your Aculab Cloud account - Level A (Level B under limited circumstances)
  • Caller ID is not owned under your Aculab Cloud account - Level B

Note that it is not currently possible for Aculab Cloud, or any CPaaS provider, to attest calls at Level A unless the caller ID is owned by the Cloud account placing the call. Level B is the highest attestation we can provide otherwise. It is hoped that future work, for example STIR/SHAKEN certificate delegation, will enable us to attest at Level A for caller IDs you own outside Aculab Cloud.