Block Spam Calls and Robocalls with Ruby

Spam, scams, and robocalls are at best annoying. For high-volume customer service centers, they can significantly impact the bottom line. Let’s leverage the Twilio Marketplace and our ruby skills to block spam callers, robocallers, and scammers.

Before getting started, you should already know how to handle incoming calls with Twilio.

Get a Spam Filtering Add-on

The Twilio Add-ons Marketplace is a great place to find Add-ons for your Twilio apps. You can integrate third-party technologies without leaving the comfort of the Twilio API. You can access the Add-ons from your Twilio Console. Today, we’re going to look at a few Voice Add-ons that can help us with this spam problem. They are, in no particular order, Whitepages Pro Phone Reputation, Marchex Clean Call, and Nomorobo Spam Score:

Voice Spam Add-ons

We’ll be writing code to work with all three of these Add-ons, but you can research which one you think will work best for your requirements. Also, keep an eye on the Marketplace, as new Add-ons are always showing up.

Installing the Add-on

Once you’ve decided on the Add-on you’d like to use, click the Install button and agree to the terms. In our use case today, we want to make use of these Add-ons while handling incoming voice calls, so make sure the “Incoming Voice Call” box for “Use In” is checked and click “Save” to save any changes:

Use in incoming voice call

Note the “Unique Name” setting. You need to use this in the code that you will write to read the Add-on’s results. In the code for this guide, we are sticking with the default names.

Check Phone Number Score in Ruby

When Twilio receives a phone call from your phone number, it will send details of the call to your webhook (more on how to configure that later). In your webhook code, you create a TwiML response to tell Twilio how to handle the call.

For spam-checking, our code needs to check the spam score of the number and deal with the call differently depending on whether the Add-on considers the caller to be a spammer or not. In our example code here, we’ll return a <Reject> TwiML tag to send spammers packing and a <Say> TwiML tag to welcome legit callers.

The code is a simple Sinatra application:

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require 'sinatra'
require 'json'
require 'twilio-ruby'
require_relative 'lib/add_ons'

post '/' do
  content_type 'text/xml'

  if params.key?('AddOns')
    Twilio::TwiML::VoiceResponse.new do |r|
      add_ons = AddOns.new(JSON.parse(params['AddOns']))
      if add_ons.call_blocked?
        r.reject
      else
        r.say('Welcome to the jungle')
        r.hangup
      end
    end.to_s
  end
end
Sinatra application using Add-ons to automatically filter spam calls
Block Spam Calls with Ruby

Sinatra application using Add-ons to automatically filter spam calls

Notice the code has checks for all three of the Add-ons we mentioned before. The code is written to be very flexible and handle missing data in the JSON response, so feel free to copy and paste even if you only plan to use one of the Add-ons. Next, we'll analyze this application in more details.

How to Check Whitepages Pro Phone Reputation

Here’s an example of what Whitepages Pro Phone Reputation will return in the “AddOns” form parameter:

Parsing that data in Ruby is done as follows:

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class AddOns
  class Whitepages
    BAD_REPUTATION = 4

    def initialize(whitepages)
      @whitepages = whitepages
    end

    def blocked?
      return false unless successful?
      result = whitepages['result']
      result && result['reputation_level'] == BAD_REPUTATION
    end

    private

    attr_reader :whitepages

    def successful?
      whitepages && whitepages['status'] == 'successful'
    end
  end
end
Make sure the Add-on processed successfully the call and use the Reputation in order to decide to block the call or not
Decide to block the call based on White Pages Pro

Make sure the Add-on processed successfully the call and use the Reputation in order to decide to block the call or not

This function uses only information found in the key results.whitepages_pro_phone_rep. Here we advise blocking the call if the reputation's level is 4.

How to Check Marchex Clean Call

Here’s an example of what Marchex Clean Call will return:

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{
  "status": "successful",
  "message": null,
  "code": null,
  "results": {
    "marchex_cleancall": {
      "request_sid": "XRxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
      "status": "successful",
      "message": null,
      "code": null,
      "result": {
        "result": {
          "recommendation": "PASS",
          "reason": "CleanCall"
        }
      }
    }
  }
}
Marchex Clean Call Add-on JSON result

Working with that data in Ruby can be handled with:

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class AddOns
  class Marchex
    def initialize(marchex)
      @marchex = marchex
    end

    def blocked?
      return false unless successful?
      recommendation = marchex.dig('result', 'result', 'recommendation')
      recommendation == 'BLOCK'
    end

    private

    attr_reader :marchex

    def successful?
      marchex && marchex['status'] == 'successful'
    end
  end
end
Make sure the Add-on processed the call successfully and followed Marchex' recommendation to decide to block the call or not
Decide to block the call based on Marchex Clean Call

Make sure the Add-on processed the call successfully and followed Marchex' recommendation to decide to block the call or not

This function uses only information found in the key results.marchex_cleancall. Here we advise blocking the call if Marchex' recommendation is set to BLOCK.

How to Check Nomorobo Spam Score

Here’s an example of what Nomorobo Spam Score will return:

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{
  "status": "successful",
  "message": null,
  "code": null,
  "results": {
    "nomorobo_spamscore": {
      "request_sid": "XRxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
      "status": "successful",
      "message": null,
      "code": null,
      "result": {
        "status": "success",
        "message": "success",
        "score": 0
      }
    }
  }
}
Nomorobo Add-on JSON result

Finally, handling that data in Ruby:

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class AddOns
  class Nomorobo
    SPAM_SCORE = 1

    def initialize(nomorobo)
      @nomorobo = nomorobo
    end

    def blocked?
      return false unless successful?
      nomorobo.dig('result', 'score') == SPAM_SCORE
    end

    private

    attr_reader :nomorobo

    def successful?
      nomorobo && nomorobo['status'] == 'successful'
    end
  end
end
Make sure the Add-on processed the call successfully and check Nomorobo Spam Score to decide to block the call or not
Decide to block the call based on Nomorobo Spam Score

Make sure the Add-on processed the call successfully and check Nomorobo Spam Score to decide to block the call or not

This function uses only information found in the key results.nomorobo_spamscore. Here we advise blocking the call if Nomorobo Spam Score is 1.

Now we've seen how to get advice from each Add-on but we have different options for handling the call. Let's look at how we're making the final decision.

Making a decision

In our example, unanimity is required for accepting a call. So for each Add-on, we look at their advice, and if even one of them tells us to block it, we'll reject the call.

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require_relative 'add_ons/marchex'
require_relative 'add_ons/nomorobo'
require_relative 'add_ons/whitepages'

class AddOns
  def initialize(add_ons)
    @add_ons = add_ons
  end

  def call_blocked?
    successful? && blocked?
  end

  private

  attr_reader :add_ons

  def successful?
    add_ons['status'] == 'successful'
  end

  def blocked?
    [marchex, nomorobo, whitepages].any?(&:blocked?)
  end

  def marchex
    Marchex.new(add_ons.dig('results', 'marchex_cleancall'))
  end

  def nomorobo
    Nomorobo.new(add_ons.dig('results', 'nomorobo_spamscore'))
  end

  def whitepages
    Whitepages.new(add_ons.dig('results', 'whitepages_pro_phone_rep'))
  end
end
Decide to accept the call only if all Add-ons are unanimous
Make a decision on blocking the call or not from all the Add-ons

Decide to accept the call only if all Add-ons are unanimous

We could have also implemented it differently by using a majority rule. In any case, once we make a decision, all that is left to do is act.

Call Handling Options

Rejection Options

Using <Reject> is the simplest way to turn away spammers. However, you may want to handle them differently. The whole universe of TwiML is open to you. For example, you might want to record the call, have the recording transcribed using another Add-on, and log the transcription somewhere for someone to review.

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require 'sinatra'
require 'json'
require 'twilio-ruby'
require_relative 'lib/add_ons'

post '/' do
  content_type 'text/xml'

  if params.key?('AddOns')
    Twilio::TwiML::VoiceResponse.new do |r|
      add_ons = AddOns.new(JSON.parse(params['AddOns']))
      if add_ons.call_blocked?
        r.reject
      else
        r.say('Welcome to the jungle')
        r.hangup
      end
    end.to_s
  end
end
Block the spammer with <Reject>

Call Accept Options

For this example, we’re just greeting the caller. In a real-world scenario, you would likely want to connect the call using <Dial> (to call another number or Twilio Client), <Enqueue> the call to be handled by TaskRouter, or build an IVR using <Gather>.

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require 'sinatra'
require 'json'
require 'twilio-ruby'
require_relative 'lib/add_ons'

post '/' do
  content_type 'text/xml'

  if params.key?('AddOns')
    Twilio::TwiML::VoiceResponse.new do |r|
      add_ons = AddOns.new(JSON.parse(params['AddOns']))
      if add_ons.call_blocked?
        r.reject
      else
        r.say('Welcome to the jungle')
        r.hangup
      end
    end.to_s
  end
end
Greet the non-spammer with <Say>

Configuring a Phone Number Webhook

Now we need to configure our Twilio phone number to call our application whenever a call comes in. So we just need a public host for our application. You can serve it any way you like as long as it's publicly accessible or you can use ngrok to test locally.

Armed with the URL to the application, open the Twilio Console and find the phone number you want to use (or buy a new number). On the configuration page for the number, scroll down to "Voice" and next to "A CALL COMES IN," select "Webhook" and paste in the function URL. (Be sure "HTTP POST" is selected, as well.)

Webhook - ngrok - root

Everything is set up now, you can pick up your phone and call your Twilio number. Hopefully, if you are not a spammer your call should be accepted and you should hear the greeting.

Testing a Blocked Call

You can quickly call your Twilio number to make sure your call goes through. However, how can we test a blocked spam result? The easiest way is to write some unit tests that pass some dummied up JSON to our controller action. For example, if we wanted to test a Nomorobo “BLOCK” recommendation, we could use the following JSON:

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{
  "status": "successful",
  "message": null,
  "code": null,
  "results": {
    "nomorobo_spamscore": {
      "request_sid": "XRxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
      "status": "successful",
      "message": null,
      "code": null,
      "result": {
        "status": "success",
        "message": "success",
        "score": 1
      }
    }
  }
}
Nomorobo Add-on JSON result (blocked)

With that as our test fixture, we can write a test like the following to ensure that our call is blocked when we see the right data in the AddOns JSON:

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require_relative 'spec_helper'

describe 'Application' do
  context 'when there are add-ons' do
    context 'and the add-on is marchex' do
      context 'and its response indicates success' do
        it 'responds with message' do
          marchex = load_json_fixture('successful_marchex.json')
          post '/', 'AddOns' => marchex
          expect(last_response.body).to say('Welcome to the jungle')
        end
      end

      context 'and its response indicates spam' do
        it 'rejects the call' do
          marchex = load_json_fixture('spam_marchex.json')
          post '/', 'AddOns' => marchex
          expect(last_response.body).to be_rejected
        end
      end
    end

    context 'and the add-on is nomorobo' do
      context 'and its response indicates success' do
        it 'responds with message' do
          nomorobo = load_json_fixture('successful_nomorobo.json')
          post '/', 'AddOns' => nomorobo
          expect(last_response.body).to say('Welcome to the jungle')
        end
      end

      context 'and its response indicates spam' do
        it 'rejects the call' do
          nomorobo = load_json_fixture('spam_nomorobo.json')
          post '/', 'AddOns' => nomorobo
          expect(last_response.body).to be_rejected
        end
      end
    end

    context 'and the add-on is whitepages' do
      context 'and its response indicates success' do
        it 'responds with message' do
          whitepages = load_json_fixture('successful_whitepages.json')
          post '/', 'AddOns' => whitepages
          expect(last_response.body).to say('Welcome to the jungle')
        end
      end

      context 'and its response contains a failure' do
        it 'responds with message' do
          whitepages = load_json_fixture('failed_nomorobo.json')
          post '/', 'AddOns' => whitepages
          expect(last_response.body).to say('Welcome to the jungle')
        end
      end

      context 'and its response indicates spam' do
        it 'rejects the call' do
          whitepages = load_json_fixture('spam_whitepages.json')
          post '/', 'AddOns' => whitepages
          expect(last_response.body).to be_rejected
        end
      end
    end
  end

  context 'when there are not add-ons' do
    it 'responds with ok' do
      post '/'
      expect(last_response).to be_ok
    end
  end
end
Uses the previous fixture to ensure we block a call not recommended by Nomorobo
Testing a blocked call with Nomorobo

Uses the previous fixture to ensure we block a call not recommended by Nomorobo

What’s Next?

As you can see, the Twilio Add-ons Marketplace gives you a lot of options for extending your Twilio apps. Next, you might want to dig into the Add-ons reference or perhaps glean some pearls from our other Ruby tutorials. Wherever you’re headed next, you can confidently put spammers in your rearview mirror.

Samuel Mendes
Orlando Hidalgo
Jose Oliveros
David Prothero
Agustin Camino

Need some help?

We all do sometimes; code is hard. Get help now from our support team, or lean on the wisdom of the crowd browsing the Twilio tag on Stack Overflow.

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require 'sinatra'
require 'json'
require 'twilio-ruby'
require_relative 'lib/add_ons'

post '/' do
  content_type 'text/xml'

  if params.key?('AddOns')
    Twilio::TwiML::VoiceResponse.new do |r|
      add_ons = AddOns.new(JSON.parse(params['AddOns']))
      if add_ons.call_blocked?
        r.reject
      else
        r.say('Welcome to the jungle')
        r.hangup
      end
    end.to_s
  end
end
class AddOns
  class Whitepages
    BAD_REPUTATION = 4

    def initialize(whitepages)
      @whitepages = whitepages
    end

    def blocked?
      return false unless successful?
      result = whitepages['result']
      result && result['reputation_level'] == BAD_REPUTATION
    end

    private

    attr_reader :whitepages

    def successful?
      whitepages && whitepages['status'] == 'successful'
    end
  end
end
{
  "status": "successful",
  "message": null,
  "code": null,
  "results": {
    "marchex_cleancall": {
      "request_sid": "XRxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
      "status": "successful",
      "message": null,
      "code": null,
      "result": {
        "result": {
          "recommendation": "PASS",
          "reason": "CleanCall"
        }
      }
    }
  }
}
class AddOns
  class Marchex
    def initialize(marchex)
      @marchex = marchex
    end

    def blocked?
      return false unless successful?
      recommendation = marchex.dig('result', 'result', 'recommendation')
      recommendation == 'BLOCK'
    end

    private

    attr_reader :marchex

    def successful?
      marchex && marchex['status'] == 'successful'
    end
  end
end
{
  "status": "successful",
  "message": null,
  "code": null,
  "results": {
    "nomorobo_spamscore": {
      "request_sid": "XRxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
      "status": "successful",
      "message": null,
      "code": null,
      "result": {
        "status": "success",
        "message": "success",
        "score": 0
      }
    }
  }
}
class AddOns
  class Nomorobo
    SPAM_SCORE = 1

    def initialize(nomorobo)
      @nomorobo = nomorobo
    end

    def blocked?
      return false unless successful?
      nomorobo.dig('result', 'score') == SPAM_SCORE
    end

    private

    attr_reader :nomorobo

    def successful?
      nomorobo && nomorobo['status'] == 'successful'
    end
  end
end
require_relative 'add_ons/marchex'
require_relative 'add_ons/nomorobo'
require_relative 'add_ons/whitepages'

class AddOns
  def initialize(add_ons)
    @add_ons = add_ons
  end

  def call_blocked?
    successful? && blocked?
  end

  private

  attr_reader :add_ons

  def successful?
    add_ons['status'] == 'successful'
  end

  def blocked?
    [marchex, nomorobo, whitepages].any?(&:blocked?)
  end

  def marchex
    Marchex.new(add_ons.dig('results', 'marchex_cleancall'))
  end

  def nomorobo
    Nomorobo.new(add_ons.dig('results', 'nomorobo_spamscore'))
  end

  def whitepages
    Whitepages.new(add_ons.dig('results', 'whitepages_pro_phone_rep'))
  end
end
require 'sinatra'
require 'json'
require 'twilio-ruby'
require_relative 'lib/add_ons'

post '/' do
  content_type 'text/xml'

  if params.key?('AddOns')
    Twilio::TwiML::VoiceResponse.new do |r|
      add_ons = AddOns.new(JSON.parse(params['AddOns']))
      if add_ons.call_blocked?
        r.reject
      else
        r.say('Welcome to the jungle')
        r.hangup
      end
    end.to_s
  end
end
require 'sinatra'
require 'json'
require 'twilio-ruby'
require_relative 'lib/add_ons'

post '/' do
  content_type 'text/xml'

  if params.key?('AddOns')
    Twilio::TwiML::VoiceResponse.new do |r|
      add_ons = AddOns.new(JSON.parse(params['AddOns']))
      if add_ons.call_blocked?
        r.reject
      else
        r.say('Welcome to the jungle')
        r.hangup
      end
    end.to_s
  end
end
{
  "status": "successful",
  "message": null,
  "code": null,
  "results": {
    "nomorobo_spamscore": {
      "request_sid": "XRxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
      "status": "successful",
      "message": null,
      "code": null,
      "result": {
        "status": "success",
        "message": "success",
        "score": 1
      }
    }
  }
}
require_relative 'spec_helper'

describe 'Application' do
  context 'when there are add-ons' do
    context 'and the add-on is marchex' do
      context 'and its response indicates success' do
        it 'responds with message' do
          marchex = load_json_fixture('successful_marchex.json')
          post '/', 'AddOns' => marchex
          expect(last_response.body).to say('Welcome to the jungle')
        end
      end

      context 'and its response indicates spam' do
        it 'rejects the call' do
          marchex = load_json_fixture('spam_marchex.json')
          post '/', 'AddOns' => marchex
          expect(last_response.body).to be_rejected
        end
      end
    end

    context 'and the add-on is nomorobo' do
      context 'and its response indicates success' do
        it 'responds with message' do
          nomorobo = load_json_fixture('successful_nomorobo.json')
          post '/', 'AddOns' => nomorobo
          expect(last_response.body).to say('Welcome to the jungle')
        end
      end

      context 'and its response indicates spam' do
        it 'rejects the call' do
          nomorobo = load_json_fixture('spam_nomorobo.json')
          post '/', 'AddOns' => nomorobo
          expect(last_response.body).to be_rejected
        end
      end
    end

    context 'and the add-on is whitepages' do
      context 'and its response indicates success' do
        it 'responds with message' do
          whitepages = load_json_fixture('successful_whitepages.json')
          post '/', 'AddOns' => whitepages
          expect(last_response.body).to say('Welcome to the jungle')
        end
      end

      context 'and its response contains a failure' do
        it 'responds with message' do
          whitepages = load_json_fixture('failed_nomorobo.json')
          post '/', 'AddOns' => whitepages
          expect(last_response.body).to say('Welcome to the jungle')
        end
      end

      context 'and its response indicates spam' do
        it 'rejects the call' do
          whitepages = load_json_fixture('spam_whitepages.json')
          post '/', 'AddOns' => whitepages
          expect(last_response.body).to be_rejected
        end
      end
    end
  end

  context 'when there are not add-ons' do
    it 'responds with ok' do
      post '/'
      expect(last_response).to be_ok
    end
  end
end