In this use case, we will show you how to automatically reject calls of callers on a blacklist. For this scenario, blacklisted phone numbers are stored in a SharePoint list. To check whether the caller is on a blacklist, we use the Web Request feature of Nimbus.

Create a SharePoint List

As a first step, create a SharePoint list with just one column named PhoneNumber and add the blacklisted phone numbers (one row each) to the list.

💡Optionally, you can also add a BlockReason column to add a note about why the phone number is on the blacklist:

After creating the SharePoint List, enable indexing for the PhoneNumber column:

1. Go to your SharePoint List.
2. In the top-right corner select “Settings → List settings”.

3. Click Indexed columns.
4. Click Create a new index. In the Primary column for this index, select PhoneNumber in the dropdown, and click Create.

💡Why enable indexing? Enabling indexing for a primary column in a SharePoint list can significantly improve performance when accessing the list via the Graph/SharePoint API, especially in scenarios involving large lists.

Create an App Registration

🔎 Also see: Quickstart: Register an application with the Microsoft identity platform | Microsoft Learn

1. Go to portal.azure.com
2. In your Tenant, Create an App registration, e.g. “My Nimbus App” 
3. Leave the other options as they are.

4. After creating the App Registration, generate a client secret as follows:
   1. Go to “Manage → Certificates & secrets”.
   2. Click “New client secret”.
      1. Add an optional Description
      2. Set the Expiration for the secret and click “Add”
   3. 🧠Now make a note of the “Value” of the generated secret as it will be needed later for the authentication.
      ☝This secret value is never displayed again after you leave this page.
5. Navigate to the “Overview” page of your App Registration and also make a note of the “Application (client) ID” as it will also be required for the authentication.

Grant Permissions 

🔎 Also see: Configure an app to access a web API - Microsoft identity platform | Microsoft Learn

1. Go to "Manage → API Permissions".
2. Click “Add a permission”.
3. Select "Microsoft Graph".
4. Select “Application permissions”.
5. Search for “sites.read.all”.
6. Expand “Sites” select the “Sites.Read.All” permission and click "Add Permissions".
7. Back In API Permissions, click “Grant admin consent for …” → Green Checkboxes signal the successful permission grant.

Get the IDs of the SharePoint Site and the SharePoint List

To get the ID of the SharePoint site:

1. Open the SharePoint List. The URL will look like this:
   1. https://<tenant>.sharepoint.com/sites/<SiteName>/Lists/<ListName>/AllItems.aspx
2. Manually remove “Lists/<ListName>/AllItems.aspx” and add “_api/site/id” to the URL. Now the modified URL should look as follows:
   1. https://<tenant>.sharepoint.com/sites/<SiteName>/_api/site/id
3. Paste the modified URL into the browser. The output you will see will be similar to this:

4. Make a note of the Id under “Edm.Guid” as that ID is the SharePoint site's ID.

Next, we need the ID of the SharePoint List:

5. Go to your SharePoint List.
6. In the top-right corner select “Settings → List settings”

7. Now look at the URL in the browser, which should look similar to this one:
   1. https://<tenant>.sharepoint.com/sites/<SiteName>/_layouts/15/listedit.aspx?List=%7B6387cfba-616e-465d-a370-54a3db11e5ea%7D
8. Make a note of the highlighted part of the URL as that ID is the SharePoint List's ID.

Creating a Parameter

In the Nimbus Admin Portal create a parameter with the name NumberFound and leave its default value empty.

We will store the answer to the web request in this parameter.

Creating the Web Request in Nimbus

First, we need to configure the authentication via the App Registration created previously:

1. Navigate to the Nimbus Admin Portal.
2. Under Configuration, select “Workflows → Authentication”.
3. Click “Create New” and provide the following information:
   1. Name: Provide a name for the authentication object. (For example, My Nimbus App auth)
   2. Organization Unit: Select an organization unit as for any other objects created in the Nimbus Admin Portal.
   3. Description: Optionally you can provide a description.
   4. Type: OAuth 2.0 Client Credentials
   5. Access Token URL: https://login.microsoftonline.com/<TenantID>/oauth2/v2.0/token
      ☝Make sure to replace the <TenantID> in the URL with the Tenant Id of your Microsoft tenant.
   6. Client ID: Here you need to specify the “Application (client) ID” of your App Registration
   7. Client Secret: Here you need to specify the Client Secret Value of your App Registration.
   8. Scope: https://graph.microsoft.com/.default
4. Once you provided all the necessary information, click Save.

Next, we create the Web Request itself:

1. Navigate to the Nimbus Admin Portal.
2. Under Configuration, select “Workflows → Web Requests”.
3. Click “Create New” and provide the following information:
   1. On the General tab
      1. Name: Provide a name for the authentication object (for example, Check Blacklist).
      2. Organization Unit: Select an organization unit as for any other objects created in the Nimbus Admin Portal.
      3. Description: Optionally you can provide a description.
   2. On the Request tab
      1. Web Request Method: GET
      2. Authentication: Select the previously created Authentication object.
      3. URL: https://graph.microsoft.com/v1.0/sites/<SiteId>/lists/<ListId>/items?expand=fields&$filter=fields/PhoneNumber eq '$(MicrosoftCallerId)'
         ☝Make sure to replace the <SiteId> in the URL with the Site Id of your SharePoint site, which you noted earlier.
         ☝Make sure to replace the <ListId> in the URL with the List Id of your SharePoint List, which you noted earlier.
   3. On the Response tab
      1. Enable Wait for Response
      2. Leave the Wait Timeout on 2000 milliseconds.
      3. Under Mapping click Add to create a response mapping with the following parameters:
         1. Parameter: Select the NumberFound parameter created earlier
         2. Response Part: Body
         3. Query Type: JSON Path
         4. Path: $.value[0].fields.PhoneNumber
      4. Click Save to save the response mapping.
4. Click Save to save the created Web Request.

Create the Nimbus Workflow

Workflow Overview

 

 

Description	Screenshot
After accepting the call, start with executing the “Check Blacklist” Web Request to check if the caller is on the blacklist. If the Web Request is successful, then we continue with a Check Parameter to check the response to the Web Request. If the Web Request times out or runs into an error, then we continue with the initial greeting in the workflow.
Witch the Check Parameter workflow activity, we check the value of the NumberFound parameter. The parameter is empty in case the phone number isn't blacklisted. If the caller is on the blacklist, then the parameter will contain the phone number of the caller. Therefore If the caller is on the blacklist, we take the Blacklisted exit of the Check Parameter workflow activity to disconnect the call. If the caller is not on the blacklist, then we take one of the others exits, which are connected to the initial greeting.