> ## Documentation Index
> Fetch the complete documentation index at: https://docs.prelude.so/llms.txt
> Use this file to discover all available pages before exploring further.

# Anti-Fraud

> Understand how Prelude's fraud prevention algorithm works, the type of fraud it prevents and how to configure it.

## How it works

Prelude’s fraud prevention algorithm is an adaptive machine learning system that assesses
the risk level of each verification in real time. It uses dozens of **signals**
relating to each verification and draws on data from our vast database to predict whether a request is
likely to be fraudulent.

Our system is flexible and responsive, continually learning from new fraud patterns and adapting to new attack vectors while granularly filtering the attacker from real users without resorting to blocking an entire country or network block.

When you make a [Verification](/verify/v2/api-reference/create-or-retry-a-verification) request,
we retrieve the data we already have on the current user and add the signals
you provide. The system then uses this information to correlate the verification
with ongoing spam attacks, bot farms, and other fraudulent activity.

## Why we built it

Who hasn't heard of a company affected by SMS fraud? Even the [biggest names](https://x.com/elonmusk/status/1626996774820024321?lang=en)
with huge engineering budgets are not immune to it.

> <Icon icon="x-twitter" /> is getting scammed by phone companies for \$60M/year of fake 2FA SMS messages

Why is this happening? Because fraud is a cat and mouse game and keeping away from
it is a constant investment. We've designed this feature to take the pressure off your engineering team, so you can concentrate on what's important: your core business.

## Configure it

To make sure that you catch all spammers during your onboarding, make sure you send all the
appropriate [Signals](/verify/v2/documentation/prevent-fraud#signals) to Prelude when sending verification requests. You can find the full
list of signals in the [API reference](/verify/v2/api-reference/create-or-retry-a-verification).