Implementing Caller ID Spoofing Prevention via STIR/SHAKEN Trust & Verify on Genesys Cloud CX

How-To-Articles
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Implementing Caller ID Spoofing Prevention via STIR/SHAKEN Trust & Verify on Genesys Cloud CX

What This Guide Covers

This guide details the configuration of Inbound Call Authentication using STIR/SHAKEN protocols within the Genesys Cloud CX environment. You will configure SIP Trunks to pass verification headers and implement Architect Flow logic to route or block calls based on attestation levels. The end result is a hardened telephony perimeter where fraudulent calls are identified in real-time and routed to a fraud queue or rejected before reaching an agent.

Prerequisites, Roles & Licensing

To execute this architecture, the following environment requirements must be met:

  • Licensing Tier: Genesys Cloud CX Enterprise License with the Trust & Verify add-on enabled. Standard CCX licenses may not expose all STIR/SHAKEN context variables required for granular routing.
  • SIP Trunk Configuration: The underlying SIP Trunk must be configured to accept and propagate STIR/SHAKEN headers from the Service Provider. This requires a carrier agreement that supports STIR/SHAKEN validation at the network edge.
  • Permissions: The user account performing configuration requires the following granular permission strings:
    • Telephony > Trunk > Edit
    • Routing > View and Routing > Edit
    • API > Read (for integration validation)
  • OAuth Scopes: If automating verification status retrieval via API, the token must include the scope view:telephony:trunks.
  • External Dependencies: A supported SIP Trunk provider that terminates STIR/SHAKEN signatures and passes them through to the Genesys Cloud platform without stripping them.

The Implementation Deep-Dive

1. Carrier Header Propagation and Trunk Configuration

The foundation of any STIR/SHAKEN implementation lies in the SIP signaling path between the carrier network and the Genesys Cloud Edge. Carriers validate the digital signature of the calling party during the initial INVITE transaction. If the signature is valid, they attach an attestation level (A, B, or C) to specific SIP headers before forwarding the call to the CCaaS platform.

In Genesys Cloud CX, you must ensure the SIP Trunk settings are configured to map these incoming headers to internal context variables. Navigate to Telephony > Trunks and select the inbound trunk responsible for PSTN termination. Locate the STIR/SHAKEN configuration section within the General tab.

You must enable the option labeled Enable STIR/SHAKEN Verification. This action instructs the Genesys Cloud media server to parse the P-Asserted-Identity and X-Signature headers provided by the carrier. Once enabled, the system maps the carrier’s attestation level to a context variable accessible within Architect Flows.

The Trap: A common misconfiguration occurs when organizations enable STIR/SHAKEN on the platform side but fail to verify that their SIP Trunk provider is actually passing the necessary headers through the edge. Many carriers strip these headers at intermediate proxies for security or legacy reasons. If the header is stripped before reaching Genesys, the context variable defaults to “Unknown” or “None,” causing legitimate high-value calls to be treated as potentially fraudulent.

The Trap Resolution: Before enabling platform settings, verify the carrier configuration. Request a packet capture (PCAP) from the carrier showing an INVITE message with STIR/SHAKEN headers intact. Ensure the header Identity-Info or X-Roaming-Indication is present in the SIP payload.

API Configuration Reference:
To confirm trunk readiness via API, perform a GET request on the trunk resource.

GET /api/v2/telephony/trunks/{trunkId}
Host: https://api.mypurecloud.com
Authorization: Bearer {access_token}
Content-Type: application/json

{
  "id": "{trunkId}",
  "name": "Inbound-PSTN-Primary",
  "type": "INBOUND",
  "domain": "sip.provider.example.com",
  "stirShakenEnabled": true,
  "headers": [
    {
      "name": "X-Verify-Status",
      "value": "attestation_level"
    }
  ]
}

The response payload confirms the stirShakenEnabled flag. If this value is false in the API response, no amount of Architect logic will process verification data because the media server does not ingest the signature.

2. Architect Flow Logic for Verification-Based Routing

Once the platform receives the STIR/SHAKEN metadata, you must implement logic to act upon it. Genesys Cloud exposes this data through context variables available within the Decision node of an Architect Flow. The primary variable is call.callerIdVerificationLevel. This variable returns one of four states:

  1. None: No signature present or not verified.
  2. Unknown: Signature present but validation failed or pending.
  3. Partial: Verified but the identity chain is incomplete (e.g., intermediate gateway).
  4. Full: The calling number is verified against a known public key infrastructure (PKI) certificate.

Navigate to Routing > Flows and edit the inbound flow handling PSTN traffic. Place a Decision node immediately after the initial Call Router. This Decision node should evaluate the call.callerIdVerificationLevel context variable.

Use the following logic expression within the Decision node:

call.callerIdVerificationLevel == "Full"

If this evaluates to true, route the call to the standard agent pool. If false, you must branch the flow to handle potential fraud. A common pattern is to route calls with a “None” or “Unknown” level to a dedicated Fraud Queue or trigger an IVR Message requesting additional verification before connecting to an agent.

The Trap: The most frequent error in this step is routing based solely on the presence of a signature rather than the quality of the attestation. A “Partial” attestation indicates the call may have passed through an unverified gateway, making it susceptible to spoofing manipulation during transit. Treating a “Partial” as “Full” defeats the purpose of the verification.

The Trap Resolution: Configure the Decision node to explicitly exclude “Partial” from the trusted path. The logic should be:

call.callerIdVerificationLevel == "Full"

Do not use wildcard matching or simple equality checks that might inadvertently capture “Unknown”. Explicitly define the accepted states.

Implementation of Fraud Handling:
For calls failing verification, create a specific branch in the Architect Flow. Use an Play Message node to play a security prompt:

  • Text-to-Speech Content: “We have detected potential spoofing on this call. Please confirm your identity by entering your account PIN.”
  • Destination: Connect to a Collect Digits node.

This forces the caller to prove their identity through a secondary channel (the phone keypad) before routing to an agent. This adds a friction layer that stops automated bots while minimizing impact on legitimate callers who can provide the PIN.

3. API Integration for Real-Time Logging and Compliance

For regulated industries such as Finance or Healthcare, storing STIR/SHAKEN verification status in call metadata is insufficient for audit trails. You must export this data to a SIEM (Security Information and Event Management) system or a compliance database. Genesys Cloud provides an HTTP Call Log endpoint that can be used for integration.

To implement this, you must configure the Call Logging settings within the Flow to include custom attributes. Create a custom attribute named stirShakenAttestation. Map this attribute to the context variable call.callerIdVerificationLevel during flow execution.

When the call terminates, the HTTP POST payload sent to your endpoint will include the verification status. Below is the JSON structure for the outbound log payload:

{
  "id": "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx",
  "direction": "INBOUND",
  "callerId": "+15550001234",
  "callTime": "2023-10-27T14:30:00Z",
  "duration": 120,
  "attributes": {
    "stirShakenAttestation": "Full",
    "verificationLevel": "FULL",
    "verifiedIdentity": true
  },
  "callStatus": "COMPLETE"
}

The Trap: A critical failure mode in this integration is the assumption that all call logs contain these attributes immediately. In high-traffic scenarios, asynchronous logging may delay the availability of these fields in your SIEM. If your fraud detection system relies on synchronous blocking logic based on the log data, you will experience false positives during peak load.

The Trap Resolution: Do not rely on the Call Log for real-time blocking decisions. Use the Architect Flow context variable for immediate routing (as described in Step 2). Use the API integration solely for post-call analytics and compliance auditing. Ensure your SIEM ingests the attributes field to correlate verification failures with specific calling patterns over time.

API Payload for Custom Attribute Definition:
To add the attribute via API, use the following request:

POST /api/v2/architect/flows/{flowId}/custom-attributes
Host: https://api.mypurecloud.com
Authorization: Bearer {access_token}
Content-Type: application/json

{
  "name": "stirShakenAttestation",
  "description": "STIR/SHAKEN verification level for compliance logging",
  "dataType": "STRING",
  "flowId": "{flowId}",
  "defaultValue": "Unknown"
}

Validation, Edge Cases & Troubleshooting

Edge Case 1: Header Stripping by Intermediate SIP Proxy

The Failure Condition: Calls appear to be routing correctly in the flow logic, but verification status is consistently “None” or “Unknown,” even for known legitimate numbers.
The Root Cause: The carrier network or an intermediate Session Border Controller (SBC) is stripping the Identity-Info header before it reaches Genesys Cloud. This often happens when calls traverse multiple SIP networks or when a VoIP provider uses legacy routing that does not support STIR/SHAKEN pass-through.
The Solution: Work with the carrier to enable “Pass-Through” mode for the specific trunk DID range. Request that they configure their SBC to preserve the Identity header in the P-Asserted-Identity field. Validate this by capturing SIP traces from the Genesys Cloud Edge and comparing them against the raw INVITE received from the carrier network. If the header is missing at the edge, the platform cannot process it regardless of configuration settings.

Edge Case 2: Routing Failures for Valid “Partial” Attestations

The Failure Condition: Legitimate calls from partner organizations or subsidiaries are being routed to the Fraud Queue because they do not have a “Full” attestation.
The Root Cause: The calling organization uses an intermediate gateway that breaks the signature chain. While the number is valid, the end-to-end cryptographic verification fails due to network topology changes. Strictly routing only “Full” attestations creates false negatives for legitimate traffic.
The Solution: Implement a whitelist mechanism within the Architect Flow. Use a Lookup Table node to check if the incoming callerId matches an internal list of approved partner numbers. If the number is whitelisted, bypass the verification level check and route directly to the agent pool. This maintains security for unknown numbers while preserving throughput for known partners who may have technical limitations in their STIR/SHAKEN implementation.
Architect Flow Logic:

// Decision Node Logic
call.callerIdVerificationLevel == "Full" OR lookupTable.check("ApprovedPartners", call.callerId)

Edge Case 3: Compliance Logging Gaps During High Load

The Failure Condition: The SIEM system does not receive STIR/SHAKEN data for a significant portion of calls during peak traffic hours.
The Root Cause: The HTTP Call Log endpoint is rate-limited or the asynchronous logging queue in Genesys Cloud is backing up. The attributes field containing stirShakenAttestation may be omitted if the payload size exceeds thresholds or if the call terminates with a specific error state that triggers a simplified log format.
The Solution: Implement a fallback mechanism within your SIEM ingestion pipeline. If the STIR/SHAKEN attribute is missing from the Call Log, query the Genesys Cloud REST API directly using the callId to retrieve the full call metadata. The endpoint /api/v2/calls/{callId} contains detailed context variables that are not always included in the standard log payload.
API Retrieval Request:

GET /api/v2/calls/{callId}
Host: https://api.mypurecloud.com
Authorization: Bearer {access_token}

// Response includes full call metadata including verification status
{
  "id": "{callId}",
  "attributes": {
    "stirShakenAttestation": "Full"
  }
}

Official References