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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.

Let's get started!

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.

How to install any Add-on

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.

Now let's check out how to implement an application using those Add-ons

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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      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 do we use Whitepages Pro?

      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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          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 do we use Marchex Clean Call?

          How to Check Marchex Clean Call

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

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              Working with that data in Ruby can be handled with:

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                  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 do we use Nomorobo Spam Score?

                  How to Check Nomorobo Spam Score

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

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                      Finally, handling that data in Ruby:

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                          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.

                          How do we finally to decide to block a call?

                          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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                              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.

                              What are our options to accept or reject a call?

                              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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                                  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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                                      How do we set up this application and test it?

                                      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.

                                      How can I test a blocked call?

                                      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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                                          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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                                              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?

                                              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 Jose Oliveros Agustin Camino Orlando Hidalgo David Prothero  Kat King

                                              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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