Verify One-Time-Passcodes (OTPs) sent via SMS text messages may not be delivered if our Fraud Guard models flag the legitimate phone number as suspicious. A legitimate phone number may be blocked if it lies between a bigger prefix block, in such scenario, the attempts will return error code 60410. You can investigate complaints from end users if their SMS are blocked by Fraud Guard viewing Blocked Verification Logs in Console.
This guide covers some workarounds you can use to help your users being affected by this block.
Notice: For delivery issues not related to Fraud Guard, please check Troubleshooting undelivered Authy and Verify SMS text messages.
Wait for the block to be lifted
Fraud guard blocks are temporary, they can range from 5 mins to up to 12 hours depending on the severity of the attack. If no further fraudulent activity is detected, the block is automatically lifted. For initial instances, it's recommended to allow the block to resolve naturally before taking any action.
Use a different channel to deliver the OTP
Verify supports other channels that can be a good alternative to users experiencing issues receiving SMS. You can implement a fall back to Voice, WhatsApp or Email for users you have certainty are legit.
Adjust the Fraud Guard protection level
Fraud Guard offers 3 protection modes that you can adjust according to your risk tolerance and the % of false positives you're willing to tolerate. If you consider your users are getting highly impacted by false positives, you can change the protection level from your Service settings. Find more in our Verify Fraud Guard FAQs.
Configure Fraud Guard Geo-Permissions
Verify geographic permissions empowers you to customize Fraud Guard settings on a country-by-country basis. If you come across a business-critical destination where you can manage the risk, you have the option to deactivate Fraud Guard for that specific geographic location. This capability can prove invaluable, especially during significant product launches when traffic to certain destinations is paramount.
Implement the RiskCheck parameter
The RiskCheck parameter allows you to override Fraud Prevention measures during the start of verification if you are confident in the reliability of the traffic. When implementing the logic for this parameter, exercise caution to ensure an optimal customer experience while maintaining security and protection.
Add the phone number to SafeList
We strongly recommend only adding user phone numbers that are verified and known to you as trustworthy, since once added, they'll never be blocked by our Fraud Prevention measures.
You can add known phone numbers to the Safe List by:
Notice: If you are experiencing continued, repeatable False Positives with Verify, please collect 5 or more logs from the last 24 hours, and then escalate these issues to our Twilio Support team.