STIR/SHAKEN statistics from September 2023

The September 2023 STIR/SHAKEN and robocall statistics are now available. The data show the latest trends in robocalls, STIR/SHAKEN participation and attestation level usage.

We’ve been publishing monthly STIR/SHAKEN statistics since April 2021. These numbers are gathered from well over a hundred voice service providers using our STIR/SHAKEN and robocall prevention solutions. The data describe calls they received from 850 other voice service providers that originated calls, including some robocalls, signed with STIR/SHAKEN.

Many robocalls are signed with B or C attestation

Sharp increase in robocalls signed with B and C attestation

Line chart comparing robocall attestations over 6 months

Figure 1. Signed Robocalls by Attestation Last 6 Months

Figure 1 shows robocalls by attestation level over the past six months. There was a sharp increase in robocalls signed with B- or C-level attestation in September. Robocalls signed B jumped from 21.21% in August to 32.46% in September. Robocalls signed C jumped from 16.18% in August to 26.78% in September. These robocall percentages reached their highest level in six months and their highest level in 2023. Robocalls among all calls rose from 6.45% in August to 8.02% in September.

STIR/SHAKEN participation

We measure STIR/SHAKEN participation changes in two ways:

  1. The number of Originating Service Providers (OSPs) signing calls received by our customers,
  2. Service providers authorized to do SHAKEN by the STI Policy Administrator (STI-PA),

SHAKEN signing leveling off

line chart showing the number of originating providers sending signed calls

Figure 2. Monthly Number of OSPs Sending Signed Calls

Figure 2 shows the number of Originating Service Providers (OSPs) signing calls. We observed 8 new SHAKEN signers in September.

The number of SHAKEN-authorized providers leveling off

line chart showing an increase in SHAKEN participation

Figure 3. STIR/SHAKEN Authorized Providers by Month

Figure 3 shows the number of SHAKEN authorized providers. As with OSP signers, this number has an upward trend that has been increasing in recent months. There were 15 new SHAKEN authorized providers in September.

These two measures show that the STIR/SHAKEN participation has leveled off.

STIR/SHAKEN coverage

STIR/SHAKEN call authentication will be more useful as the percentage of signed calls received at termination and calls with full A-level attestation increases. We had been observing slow, steady improvement over the past six months, but both measures of coverage were down in August and rebounded only slightly in September.

Signed calls at termination leveling off

line chart showing the percentage of signed calls received at termination

Figure 4. The Percentage of Signed Calls at Termination Last 6 Months

Figure 4 shows the percentage of signed calls at termination for the past six months. This figure had been slowly increasing, reaching 34% in July. This number dropped almost 3% in August and rebounded 0.5% in September. We suspect that this number remains low because widespread non-IP interconnections in call paths cause STIR/SHAKEN information to be lost. Non-IP STIR/SHAKEN methods exist, but they have not been mandated for use.

Calls with full attestation up slightly

line chart showing the percentage of calls received at termination by attestation level

Figure 5. Percentage of Calls with SHAKEN Attestation Levels Last 6 Months

Figure 5 shows that the percentage of calls signed with full attestation had been climbing over the past six months, reaching 24.5% in July. This figure dropped 21.5% in August and rebounded slightly to 22.5% in September.

analytics charts on a computer

Patterns among prolific robocall signers

Here are robocall and attestation statistics for the top 10 SHAKEN-authorized providers ranked by the percentages of signed calls identified as robocalls.

Prolific robocall signers increase robocalls among A- and B-level calls

robocalls among calls with A-level attestation are increasing

Figure 6. Robocall Percentage by Attestation—Prolific Robocall Signers by Robocall %

Figure 6 shows a steady increase of robocalls signed with A- and B-level attestation by prolific robocall signers. Among these prolific robocall signers, 88.46% of calls they signed with B-level attestation and 79.4% of calls they signed with A-level attestation were robocalls. Robocalls among calls signed with C-level attestation continue their downward trend.

We believe that terminating service providers and their subscribers would benefit by adapting their call analytics to evaluate the reputation of STIR/SHAKEN signers.


  • Robocalls signed with B- and C-level attestation jumped sharply.
  • Robocall percentages among the top 10 prolific robocall signers were up among A- and B-level attestation calls.
  • STIR/SHAKEN participation leveled off.
  • STIR/SHAKEN coverage dropped unexpectedly in August and rebounded slightly in September.

TransNexus solutions

TransNexus is a leader in developing innovative software to manage and protect telecommunications networks. The company has over 25 years’ experience in providing telecom software solutions including toll fraud prevention, robocall mitigation and prevention, TDoS prevention, analytics, routing, billing support, STIR/SHAKEN and SHAKEN certificate services.

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