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  • Gulshanpreet Singh

Robocalls: The END is near

What is a Robocall?

A robocall is a phone call made by an automated computer program, commonly referred to as a "robot" or "bot." These calls are typically pre-recorded messages that are delivered to a large number of recipients simultaneously, often for various purposes, such as political campaigns, telemarketing, debt collection, or scams.

Robocalls are frequently used for legitimate purposes, such as automated appointment reminders from healthcare providers or informational messages from government agencies. However, they are also commonly associated with unwanted and intrusive calls, such as telemarketing pitches, fake IRS or Social Security scams, and other fraudulent activities.

Over the past few years, robocalls have rapidly overwhelmed the telephone world. According to a study analyzing over 50 million calls, the number of robocalls is dramatically increasing, from 3.7% of total calls in 2017 to 29.2% in 2018. And it’s projected to reach 44.6% by 2019. This article discusses the current solutions available to consumers that are provided by telephone service providers to prevent robocalls. It also includes the newly adopted SHAKEN/STIR standard for caller ID identification by service providers. SHAKEN/STIR standard refers to the criteria of using public key infrastructure to authenticate the calls between the originating and terminating service providers.

On July 24, the House of Representatives approved an anti-robocalling bill, dialing up the heat that Congress has been pressing on telecoms and the Federal Communications Commission due to the onslaught of harmful calls. As a result, the US Federal

Telecommunications Committee which has been pushing for SHAKEN/STIR's adoption has imposed the end of 2019 as a hard deadline for networks implementing the protocol. Though research and development teams at AT&T and Comcast have claimed to have completed the first SHAKEN/STIR call made between two different networks, the U.S. has already been hit with 33 billion robocalls this year.

Robocalls are irrelevant or inappropriate messages sent over the phone to a large number of recipients – typically to those who have not expressed interest in receiving the message. Caller forces the users to pick the calls using Caller ID spoofing. Spoofing is when a caller deliberately falsifies the information transmitted to a user’s caller ID display to disguise their identity. Scammers often use neighbor spoofing so it appears that an incoming call is coming from a local number, or spoof a number from a company or a government agency that users may already know and trust. Not only are spam calls annoying, they are very dangerous. Without a solution to effectively stop the flood of unwanted spam calls received on their smartphone, users are vulnerable to phone scams and the crooks responsible for them.

Present Solutions to Combat Robocalls

The major wireless companies all provide free and paid services that can alert customers to suspected robocalls or block them. AT&T’s Call Protect app provides fraud warnings, and spam call screening and blocking. Call Protect is free for iOS and Android. AT&T also offers Call Protect Plus for $3.99 a month which offers enhanced caller ID services and reverse number lookups.

Sprint also lets customers block or restrict calls through its Premium Caller ID service. It costs $2.99 per month and can be added to a Sprint account. On the other hand, T-Mobile already lets customers know when an incoming call is fishy by displaying “scam likely” as the caller ID. Users can also ask T-Mobile to block those calls before the phone even rings using Scam Block. Customers can get it for free by dialing #662# from their device.

Verizon‘s Call Filter is an app that works on both iOS and Android. The free version detects and filters spam calls, while it's $2.99 a month version gives users a few additional features like its proprietary “risk meter” to help them know more about the caller.

Third-party apps are also widely available and often free. They’re the best tools available right now. These apps include Hiya, YouMail, Robokiller, TrueCaller and Nomorobo. There isn’t a lot one can do for traditional landline phones, except block individual phone numbers.

SHAKEN/STIR - Called ID Authentication

Caller ID authentication is a new system aimed at combating illegal caller ID spoofing and spam calls. Industry stakeholders are working to implement caller ID authentication, which is called SHAKEN/STIR. SHAKEN/STIR, Signature-based Handling of Asserted Information Using Tokens (SHAKEN) and the Secure Telephone Identity Revisited (STIR) standards, is a framework of interconnected standards. An originating service provider puts the call on the network and authenticates the caller ID information using STIR/SHAKEN. Service providers know their customers, so they’re well-positioned to do that. They secure their authentication by signing the call using public key infrastructure, which is also widely used with the internet. A terminating service provider delivers the call to their customer and also verifies the caller ID information in the call using the public key infrastructure to confirm the information and signature still match. The following call flow diagram illustrates how STIR/SHAKEN works:

1. A SIP (Session Initiation Protocol) INVITE is received by the originating telephone service provider.

2. The originating telephone service provider checks the call source and calling number to determine how to attest to the validity of the calling number.

  • Full Attestation (A) — The service provider has authenticated the calling party and they are authorized to use the calling number. An example of this case is a subscriber registered with the originating telephone service provider’s softswitch.

  • Partial Attestation (B) — The service provider has authenticated the call origination, but cannot verify the call source is authorized to use the calling number. An example of this use case is a telephone number behind an enterprise PBX.

  • Gateway Attestation (C) — the service provider has authenticated from where it received the call, but cannot authenticate the call source. An example of this case would be a call received from an international gateway.

3. The originating telephone service provider uses the authentication service to create a SIP Identity header. The authentication service could be a third-party service hosted in the cloud a software application integrated with the telephone service provider’s softswitch or Session Border Controller (SBC). The SIP Identity header contains the following data:

  • Calling number

  • Called number(s)

  • Current timestamp

  • Attestation level

  • Origination identifier

4. The SIP INVITE with the SIP Identity header is sent to the terminating telephone service provider. In addition, the Identity token may be sent across the internet, out-of-band, to the terminating provider’s Call Placement Service.

5. The SIP INVITE with the Identity header is passed to the verification service.

6. The verification service obtains the digital certificate of the originating telephone service provider from the public certificate repository and begins a multi-step verification process. If all verification steps are successful, then the calling number has not been spoofed.

  • The SIP Identity header is base64 URL decoded and the details are compared to the SIP INVITE message.

  • The public key of the certificate is used to verify the SIP Identity header signature.

  • The certificate chain of trust is verified.

The verification service returns the results to the terminating service provider’s softswitch or SBC.'

Top Patent Assignees - Robocall

NEC, Panasonic, and Fujitsu are top patent holders for robocalls because they are all major telecommunications companies with a long history of developing and deploying telecommunications technology. The global robocall market is expected to reach $100 billion by 2025. This growth is being driven by the increasing use of robocalls for a variety of purposes, including telemarketing, fraud, and political campaigning.

The development of new robocall technologies is likely to play a major role in the growth of the robocall market. NEC, Panasonic, and Fujitsu are well-positioned to benefit from this growth, as they are among the leading developers of robocall technology.

Top Patent Application Countries

Seminal Patents - Robocall


Determining and denying call completion based on the detection of robocall or telemarketing call

Original Assignee: TelTech Systems Inc.

Current Assignee: TelTech Systems Inc.

It relates to a method for handling an incoming call, comprising the steps of determining that the incoming call is an unwanted call. The process included locating at least one prior call where the characteristics of a calling party match that of the unwanted call, determining an audio response which kept the calling party in the prior call longest and playing the audio response which kept the calling party in the prior call longest in the unwanted call.

Before forwarding the call to intended recipient, the call is routed within a switch. First, phone number of calling party is checked the call is answered by the switch at this point. A continued ringing sound is played to the calling party, a greeting or a request for a name to be stated. Meanwhile, when answering the call, the audio received from the calling party is compared to prior stored audio in a database. Then signatures stored such as the audio signatures transcribing the voice recording of the call are compared to further determine if the call is an unwanted robocall or telemarketing cal


Method for blocking illegal prerecorded messages

Original Assignee: John Almeida

Current Assignee: Unoweb Inc.

This patent proposes a method for blocking illegal prerecord messages (robocalls). The method uses telephone number lists and a telephone exchange server to enable the blocking of illegal robocalls and to enable the legal ones to proceed free of impediment. The method includes the following steps:

1. Server computer receiving a request to permit a telephone call to the first telephone when the telephone call originates from a second telephone number;

2. Storing the first telephone number and the second telephone number;

3. Intercepting a call to the first telephone number and determining an originating telephone number for a device making the intercepted call;

4. Comparing the originating telephone number to the telephone number list and if the originating telephone number is in the telephone number list, then the server computer enables the call to ring at the first telephone.


Determining and denying call completion based on detection of robocall or unsolicited advertisement

Original Assignee: TelTech Systems Inc.

Current Assignee: TelTech Systems Inc.

The method proposed prevents the receipt of unwanted calls by determining an intermediate switch between calling party and called party. If the calling party is in the database of previously verified callers, the call is passed on to the called party. If not, then the calling party is prompted to provide data, such as "press 5 to be connected' or “say proceed’ before being allowed to connect. Once connected, the called party may indicate that the call was/is unwanted and should be disconnected. Then, the call is disconnected from the called party while being maintained with the switch. The call is also recorded to detect future unwanted calls. The detection of future unwanted calls may be modified based on association of called parties to each other which further may be used to change the threshold of closeness of audio signatures between calls.

Rules and Regulations to Combat Robocalls

The United States has implemented several rules and regulations to combat robocalls and protect consumers from unwanted and potentially fraudulent calls. These rules include:

  1. Telephone Consumer Protection Act (TCPA): The TCPA is a federal law that restricts telemarketing calls and the use of automated dialing systems, prerecorded messages, and artificial or prerecorded voice calls. It also requires telemarketers to maintain a "Do Not Call" list and honor the National Do Not Call Registry.

  2. National Do Not Call Registry: The Federal Trade Commission (FTC) maintains the National Do Not Call Registry, where consumers can register their phone numbers to opt out of receiving unsolicited telemarketing calls. Telemarketers are required to check this registry and refrain from calling registered numbers.

  3. Robocall Mitigation: The Federal Communications Commission (FCC) has implemented rules to require phone service providers to implement robocall mitigation measures, including the implementation of the STIR/SHAKEN framework to authenticate caller ID information and reduce spoofed calls.

  4. Truth in Caller ID Act: This federal law prohibits the use of misleading or inaccurate caller ID information with the intent to defraud, cause harm, or wrongfully obtain anything of value.

  5. Enforcement Actions: Federal and state agencies, including the FTC and FCC, take enforcement actions against individuals and organizations engaged in illegal robocall activities. These actions can result in substantial fines and penalties.

  6. Call Blocking and Screening: Many phone service providers offer call blocking and screening services to help consumers filter out unwanted robocalls and spam calls.

  7. Call Authentication Technologies: The implementation of call authentication technologies like STIR/SHAKEN (Secure Telephone Identity Revisited/Signature-based Handling of Asserted Information Using Tokens) helps verify the authenticity of caller ID information, making it more difficult for robocallers to spoof phone numbers.

  8. Consumer Reporting: Consumers are encouraged to report unwanted robocalls to the FTC and FCC, as well as to their phone service providers, to aid in tracking and enforcement efforts.


In the future, robocalls are expected to face a landscape characterized by increasingly stringent regulations and enhanced enforcement efforts, as governments worldwide respond to the growing nuisance of unwanted calls. Technological advancements will play a pivotal role, with call authentication technologies like STIR/SHAKEN becoming more prevalent and AI-driven call filtering tools continuing to improve. Telecommunication companies are likely to implement carrier-level solutions to block robocalls at the source. Additionally, consumer awareness will rise, making it more challenging for scammers to succeed. Meanwhile, fraudsters will adapt by using more sophisticated tactics, such as convincing voice synthesis and personalized content. International collaboration and legal actions against large-scale robocall operations will increase, while consumer empowerment through call-blocking apps and reporting mechanisms will continue to grow. Despite these developments, the battle against robocalls will remain an ongoing challenge, marked by a dynamic interplay between regulatory efforts, technology innovations, and the evolving strategies of malicious actors.

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