---
title: "How to Approve Real Users and Block Fake Accounts at Sign Up with Lookup and Verify in C#"
description: "Fake accounts and fraudulent sign-ups motivate a C# onboarding flow that screens phone numbers before sending an OTP. It combines Twilio Lookup line type intelligence, optional line status checks, and Identity Match with Twilio Verify phone verification. The pipeline rejects landline, nonfixed VoIP, toll-free, and pager types, requires first- and last-name results of exact_match or high_partial_match, and can reject lookup failures or mismatches. The post supplies a .NET 9 project setup, environment variables, MVC files, and service code for starting and checking verification. It reports example logs for a mobile number with active status and exact name matches, demonstrates blocked toll-free or VoIP testing, and notes that Lookup and Verify pricing varies by package and country."
---

# How to Approve Real Users and Block Fake Accounts at Sign Up with Lookup and Verify in C#

[Twilio](https://yomu.fyi/company/twilio) · Amanda Lange, Dhruv Patel, Kelley Robinson · Aug 28, 2026

**Type:** Tutorial

## Summary

Fake accounts and fraudulent sign-ups motivate a C# onboarding flow that screens phone numbers before sending an OTP. It combines Twilio Lookup line type intelligence, optional line status checks, and Identity Match with Twilio Verify phone verification. The pipeline rejects landline, nonfixed VoIP, toll-free, and pager types, requires first- and last-name results of exact\_match or high\_partial\_match, and can reject lookup failures or mismatches. The post supplies a .NET 9 project setup, environment variables, MVC files, and service code for starting and checking verification. It reports example logs for a mobile number with active status and exact name matches, demonstrates blocked toll-free or VoIP testing, and notes that Lookup and Verify pricing varies by package and country.

## Context

The signup flow is intended to block bots, fake accounts, and signup fraud while providing real users with a seamless path and higher pass rates.

## Approach / What changed

The implementation orchestrates Twilio Lookup and Verify in progressively stronger checks: line type intelligence, optional line status, name-to-number Identity Match, and an OTP-based phone verification flow. It uses a .NET 9 MVC project, C# service code, environment variables, and a Verify Service SID.

## Takeaways

- Line Type Intelligence blocks landline, nonfixed VoIP, toll-free, and pager numbers before later verification steps.
- Identity Match accepts exact\_match or high\_partial\_match for both first and last names; no\_match, partial\_match, or null results are rejected.
- The flow orders cheaper Lookup checks before more expensive Identity Match and Verify calls, with pricing varying by package and country.

**Tags:** [Authentication](https://yomu.fyi/topic/authentication), [Twilio](https://yomu.fyi/topic/twilio)

- Source: [Twilio](https://www.twilio.com/en-us/blog/developers/tutorials/product/block-fake-accounts-lookup-verify-csharp)
- Source URL: https://www.twilio.com/en-us/blog/developers/tutorials/product/block-fake-accounts-lookup-verify-csharp
- Ingested by Yomu: 2026-09-09T13:35:51.639Z

[Read original post](https://www.twilio.com/en-us/blog/developers/tutorials/product/block-fake-accounts-lookup-verify-csharp)