The RoboBlaster blocks 95% of illegal robocaller calls to the consumer “on the fly”.

The Roboblaster functions identically for every consumer of plain old telephone service (POTS), voice over IP (VoIP) and cellular telephone service to any device that uses push buttons for DTMF tones to dial a number.

Over a 30-day trial period during the preparation of this proposal, none of the illegal robocaller calls the proposal writer received on his home phone had valid and complete Caller ID information; conversely, all of the legal robocaller calls did have valid and complete Caller ID information. This finding is the key to blocking the illegal robocaller.

The process to block at least 95% of illegal robocallers for all consumers is performed in four steps:

  1. Apply a list-based blocking algorithm to block all known illegal robocallers based upon a number of caller lists. If an incoming call is not a reverse 911 call, the Caller ID is first compared to entries in an Individual White List, and next to entries in an Individual Black List, and finally to entries in a Service Provider Black List. If the Caller ID is found in the white list, the call is completed. If the Caller ID is found in either black list, the call is blocked. The Service Provider Black List also incorporates the caller’s service provider information if it is available. If the caller appears in none of these lists, the blocking process continues to the next step.

  2. Apply extensions to the blocking algorithm to block unknown illegal robocallers “on the fly” by analyzing the Caller ID to determine if the caller is misrepresenting itself to the recipient. If the Caller ID is erroneous or contains certain keywords, the incoming call is blocked; otherwise, the call is completed.

  3. Identify new illegal robocallers by analyzing Individual Black Lists of the entire customer base for identical reports from multiple call recipients and verifying those reports. The service provider periodically analyzes their customers’ individual black lists for common additions by large numbers of customers to identify suspected illegal robocallers to verify. If the verification process determines that a robocaller is illegal, the robocaller information is added to the Service Provider Black List. If the verification process determines that a robocaller is legal, the robocaller information is added to the Service Provider Allowed List.

  4. Update the Individual Black List, the Service Provider Black List and the Service Provider Allowed List continuously. Share the Service Provider Black List and the Service Provider Allowed List updates with other service providers, and incorporate updates to these lists from other service providers.

The Service Provider Black List has been substantially borrowed from the Internet community. This black list strategy is proven through years of use for e-mail service, and it is adaptable to the telephone industry.

The Service Provider Black List is fundamentally important to the blocking strategy. As the illegal robocaller changes Caller ID numbers and service providers to avoid blocking tools, the Service Provider Black List is continuously updated by the service provider community to defeat the known illegal robocaller.

The Blocking Algorithm Extensions are fundamentally important to defeating obvious spoofing ploys on the fly. The blocking algorithm extensions are analogous to an e-mail spam filtering application a PC user might purchase and install.

The most troubling threat from the illegal robocaller to defeat the RoboBlaster or any other list-based blocking strategy is a hack to steal Individual White Lists to utilize for spoofing Caller IDs for robocalls directed to each Individual White List owner. Illegal robocaller sophistication does not currently expose this vulnerability, but it surely will in time.


In its blocking operation, the Roboblaster is invisible to the consumer except for a simple process for the consumer to report suspected illegal robocallers that get past the blocking algorithms (the other 5%) immediately after the consumer hangs up their phone. From this perspective, it is identical to the existing phone feature that the recipient uses to command their service provider to block all future calls from the caller just received by pressing a simple sequence of buttons on their phone.

Tools currently in place for white list and black list building are efficient, easy to use, and satisfactory for user communities including users with a variety of disabilities. Numerous time-proven options currently exist for list configuration and maintenance.

Typos and keypad errors by the user maintaining their individual white list and black lists have limited impact. The most severe error is for a user to configure their Individual Black List from their “white list” phonebook. A list reset would resolve that error easily and conveniently for the error-prone user.


Deployment is realistic. More than half of the solution to block at least 95% of illegal robocallers already exists with the service provider today, and the most beneficial elements of the proposal such as the Caller ID, the Individual White List and the Individual Black List are deployable today without any additions to the telephone network infrastructure. The Caller ID is a universal feature of every telephone voice service currently deployed in the United States, and it has been proven over decades of network deployment. These first steps toward the RoboBlaster implementation achieve a successful blocking “hit rate” of 50% or more. All that is required is for the service provider to make the Individual Black List feature available to all of their customers and extend the current feature by removing the limit for the number of callers blocked.

Deployment is economically feasible. Deployment of a Service Provider Allowed List and a Service Provider Black List are no more difficult or costly than the individual white list and black list features currently in use in the telephone industry and Internet industry.

Deployment relies primarily on the service provider. It is essential that the service provider is able to perform all of the processing necessary to block illegal robocallers. An important element of the proposed robocaller blocker includes the collection and analysis of network path trace information to augment the analysis of the Caller ID. The network path trace is available from the recipient’s service provider’s network management systems, and this information identifies the robocaller’s service provider at the network-to-network interface with other service providers’ networks. The network path trace information is not passed to the recipient’s telephone device, however, and this aspect of the blocker solution is the underlying reason that the service provider must perform the list-based processing to block illegal robocallers. The Network Path Trace is essential to identify stolen Caller IDs.

Incorporating the Service Provider Black List with Caller ID in conjunction with caller service provider information extends the successful blocking “hit-rate” even further to 80% of more. This step of the solution can be accomplished in as little as six months and be effective with a useful baseline of illegal robocallers to block in another six months.

Extending the blocking algorithm for anonymity, syntax and context analysis achieves a 95% successful blocking “hit rate” is likely to be difficult and time consuming, demanding between one and two years to put first implementations in place.

Through the clever design of the sequence of processing, blocking and list maintenance that is proposed, more than 95% of illegal robocaller calls will be blocked in short order for every telephone service consumer of plain old telephone service (POTS), Voice over IP (VoIP) and cellular service. The proposed algorithm to block illegal robocallers assures completion of Reverse-911 calls and avoids erroneously blocking legal robocallers and desired callers. The Roboblaster is easy to use, and it can be rolled out economically by the service provider.

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