Robocall mitigation is the ability to stop illegal robocalls. While it may seem obvious on how to do this, determining an illegal robocall is not simple.  While most of us consider a majority of robocalls as illegal, there is a significant percentage of use cases where robocalls are considered acceptable and legal.  Therefore, any solution that addresses robocall mitigation should be based on reasonable analytics to ensure that bad calls are stopped, but good calls are allowed to proceed.

  • Originating robocall mitigation stops Illegal robocalls at the originating switch.  Originating robocall mitigation is an important aspect of reducing illegal robocalls and has been mandated by the FCC for voice service providers in the US.  Unfortunately, many illegal robocalls are originated in countries that do not have similar regulatory mandates, making originating robocall mitigation only part of a larger solution.
  • Terminating robocall mitigation stops illegal robocalls in the terminating network. Because it is possible for malicious robocalls to make it to the terminating network, blocking these calls before call termination is extremely valuable. Furthermore, this ability to block robocalls with malicious intent must to available for both TDM and IP switches.

As an incumbent supplier to many of the voice service providers who are trying to address illegal robocalls, Ribbon’s Call Trust® portfolio was developed to give a service provider the tools to identify potential illegal robocalls, determine the degree of risk associated with the robocall, and as required the ability to stop an illegal robocall before it negatively affects a business or end user.

Originating Robocall Mitigation – FCC Mandates

In the US, the FCC expects voice service providers to "Know Your Customer"  As such, the FCC has made multiple rulings that directly address originating robocall mitigation:


On September 29, 2020, in FCC 20-136, the FCC granted a 2-year extension to the deadline for implementation of Caller ID authentication (STIR/SHAKEN) for many smaller voice service providers. Accompanying this extension was an obligation to take affirmative, effective measures to prevent new and renewing customers from using their networks to originate illegal robocalls.  The FCC did not specify the attributes of such an originating robocall mitigation program but did indicate voice service providers would have to file information on how they would meet this obligation in an FCC-maintained database
On December 29, 2020, in FCC 20-187, the FCC further affirmed the requirement that voice service providers adopt affirmative, effective measures to prevent new and renewing customers from using their network to originate illegal robocalls
On April 20, 2021, the FCC announced the opening of their Robocall Mitigation database with instructions that all voice service providers must file the details of their STIR/SHAKEN implementation or their originating robocall mitigation program by June 30, 2021.
On Sept 28, 2021, downstream voice service providers were mandated to not terminate traffic from any upstream service provider who does not have a valid entry in the FCC Robocall Mitigation database.  That makes the penalty for non-compliance pretty costly.

Identity Assurance Explained

Ribbon Reputation Scoring - Originating Robocall Mitigation

You can meet the FCC mandate for originating robocall mitigation by subscribing to Ribbon’s cloud-hosted Reputation Scoring service.

For each originating call, in real-time as part of the call routing process, Ribbon’s Reputation Scoring service will be queried to determine the likelihood that the call is legitimate vs. illegitimate. The query may be invoked via SIP signaling or via a REST API.

Reputation Scoring uses machine learning models to analyze each call attempt and provides multi-dimensional reputation scores and guidance for call validation treatment.  For example:

  • If an originating call is using a spoofed telephone number (TN) that appears on a Do-Not-Originate list or is an unallocated, unused, or invalid number, it will be identified as illegal and should be blocked at the originating switch. These are the easy calls to address
  • For bad actors spoofing valid TNs, Reputation Scoring analyzes the call vs. normative traffic patterns. If there is a reasonable likelihood that the call is being made with malicious intent, it will instruct the originating switch to block the call. For all other calls, the originating switch will be instructed to route advance the call, so it proceeds normally to its destination.
Ribbon Reputation Scoring Graphic

Ribbon Reputation Scoring For Originating Robocall Mitigation

Robocall Mitigation Rep Score Diagram

Ribbon Originating Robocall Mitigation

Terminating Robocall Mitigation – FCC Guidance

Terminating robocall mitigation is the ability to identify and stop illegal robocalls in the terminating network.  In the US, the FCC mandated originating robocall mitigation rather than terminating robocall mitigation, but they did recognize the value and usefulness of terminating robocall mitigation. As such, they provided guidance in several rulings, first in FCC 20-96 (July 16, 2020) and then with clarification in FCC 20-187 (December 29, 2020),  where they stated:

Voice service providers that block calls or utilize caller ID authentication information in determining how to deliver calls must:
  • Not block a voice call placed to 911 and not block a voice call from public safety answering points and government emergency numbers
  • Provide a single point of contact for receiving call blocking error complaints and verifying the authenticity of the calls
  • Resolve caller ID authentication information disputes within a reasonable time and, at minimum, provide a status update within 24 hours
  • Stop blocking if a caller makes a credible claim of a call blocking error, or the terminating provider determines that the calls should not have been blocked, or the call delivery decision is not appropriate
  • Not impose any charge on callers for reporting, investigating, or resolving complaints made in good faith
Terminating providers may block calls without liability under the Communications Act and the Commission’s rules and without giving consumers the opportunity to opt out of such blocking, so long as the provider:
  • Uses reasonable analytics and caller ID authentication information where available to identify and target calls that are highly likely to be illegal
  • Manages the call blocking with human oversight and network monitoring to make sure blocking is working as intended
  • Stops blocking calls determined to be likely lawful
  • Notifies customers it is engaging in call blocking
  • Applies all analytics in a non-discriminatory, competitively neutral manner
  • Provides blocking services with no additional line-item charge to consumers

Ribbon Reputation Scoring For Terminating Robocall Mitigation In IP Networks


Ribbon Reputation Scoring For Terminating Robocall Mitigation In TDM Networks

Terminating Robocall Mitigation For TDM Networks