Robocall Prevention: STIR/SHAKEN and Call Blocking

The world over hates robocalls. The telecommunications industry and regulatory bodies are taking action to combat them. Central to solving one of the robocall challenges is a new standard called STIR/SHAKEN. But call blocking is needed too, and there are solutions for that available today. Alianza is addressing both requirements.

What are Robocalls?

Robocalls are auto-dialed calls that contain a message made with a prerecorded or artificial voice. Some of these calls are legitimate, like school closure announcements or appointment reminders, but not all of them are. The FTC says “a robocall trying to sell you something is illegal unless a company has your written permission to call you that way.”

Not only do robocalls annoy us, but many also attempt to defraud people of money. Some are more sophisticated and can even mimic a conversation with speech recognition and automated responses.

Unwanted calls, including illegal and spoofed robocalls, are the FCC’s top consumer complaint (with over 200,000 complaints each year, around 60 percent of all complaints received) and their top consumer protection priority. There are many resources showing the growing number of fraudulent or unwanted calls. For instance, the YouMail Robocall Index produces monthly nationwide robocall data for the U.S.—February 2020 saw 166.3 MILLION calls per DAY!

Many robocallers use “spoofed” or fake caller IDs to appear to be a local number or even a known number, so that familiarity will drive more people to answer those calls.


Ways to Combat Robocalls

The FCC has a multi-faceted approach to combat robocalls, as does the telecom industry, including 1) making sure the caller is who they claim they are, and 2) blocking known illegal or malicious calls. The former is the focus of the evolving industry standard called STIR/SHAKEN.



STIR, or Secure Telephony Identity Revisited, introduces a trust value score in the signaling (SIP messages) that set up VoIP calls. SHAKEN, the acronym for Signature-based Handling of Asserted information using toKENs, is a suite of guidelines that indicate how service providers should deal with calls with STIR information as they cross networks.

Together, these new standards introduce new authentication technology to verify calls routed between networks. As calls are attempted, there’s an exchange of information that examines the caller ID information and gives it a rating of reliability, or attestation, that the caller is who they say they are. Incoming calls are given a low, medium, or high attestation rating, and carriers will determine how they will react to lower levels or present that to the called party. As it stands now, STIR/SHAKEN itself is not a blocking solution.

Read more about what it is and how it works in Bandwidth’s handy STIR/SHAKEN guide.

STIR/SHAKEN is an integral part of the U.S.’s TRACED Act of 2019, which aims to curb the rise in malicious robocalling and illegal spoofing. The TRACED Act mandates that service providers implement STIR/SHAKEN by June 2021. The FCC believes that “industry-wide implementation would reduce the effectiveness of illegal spoofing, allow law enforcement to identify bad actors more easily, and help phone companies identify calls with illegally spoofed caller ID information before those calls reach their subscribers.” The CRTC will also likely mandate this technology in Canada; an initial proposal from the organization in December 2019 submitted September 2020 as the implementation date, but there is pushback from communication service providers on the feasibility of that deadline.

A notable drawback in today’s proposed approach is that it will only work on VoIP networks and any legacy TDM network in the chain will break the inter-carrier authentication. Also, simply forwarding a call will also disrupt the verification chain. While most wireline phones are VoIP (see The State of Wireline Phone and VoIP in the U.S.), there are still tens of millions of legacy TDM telephone lines, and new developments will be needed to support those lines.

Another drawback is that only tier 1 carriers (those who procure phone numbers directly from the numbering authority) are entitled to certificates and there is not a clear standard on how they will delegate those certificates to their resellers and cloud communication platform providers such as Alianza who can more accurately attest to the identity of the actual calling party.


Alianza’s Plan for STIR-SHAKEN

Alianza is committed to implementing a STIR/SHAKEN solution according to the rules and timelines. In addition to being a telecom regulation, it’s good for end users. Our solution will be tightly aligned with the tier 1 carriers, so we are actively working with our carrier partners on this solution. We will implement a yet-to-be-determined solution in which Alianza can provide that all levels of attestation as well as options for end users on how to treat calls received by lower levels of attestation.


Going Beyond STIR/SHAKEN with Call Blocking

Once STIR/SHAKEN is actively implemented across the industry, unverified calls will be blocked or passed on with warnings. Robocallers could still slam end users with calls, they just now have a verified caller ID, so presumably, the live connections will decrease.

Verifying the legitimacy of robocalls may be getting easier, but call blocking is still necessary. Alianza has partnered with Nomorobo to provide a call blocking solution; this solution has been available since 2016. It blocks >95% of unwanted calls and it’s free for our CSP customers’ residential end users. We are also looking to enhance that integration or use other data-based blocking solutions. Alianza believes combatting robocalls will require a long-term, permanent, multi-pronged approach to protect end users from unwanted robocalls.

Customers: read more about our NoMoRobo implementation in the Help Center or contact your customer success manager for more info on extending the NoMoRobo blocking solution to your customers.