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

# Set up fraud prevention rules

> Set up fraud prevention rules in Stripe alongside Memberful's defaults to protect your business from credit card testing, credential stuffing, and other fraud.

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Memberful requires a Stripe account to process credit card payments. Stripe offers a powerful tool called [Radar,](https://stripe.com/docs/radar/rules) which lets you create fraud prevention rules to automatically review, block, or allow payments that match specific criteria.

In this help article, we'll walk through how to enable the following rules to help defend against fraudulent activity—especially credit card testing and credential stuffing.

## Set up rules for new businesses

If you're just launching your business and have no paying members yet:

1. Log in to Stripe and go to *Payments → Rules.*
2. Enable the following 3D Secure rules:
   * Request 3DS if 3D Secure is required for card.
   * Request 3DS if 3D Secure is recommended for card.
3. Set up these Radar rules:
   * Block if CVC verification fails.
   * Block if postal code verification fails.
4. If you offer a free trial, enable *Use Radar on payment methods saved for future use.*

This costs 5¢ per attempt, but it helps prevent abuse and preserves a free trial experience. Alternative: Consider switching to a [paid trial model](/plans/individual-plans/create-a-plan/#enable-free-or-paid-trials) for added protection.

Need help setting up rules? [Contact Stripe support.](https://support.stripe.com/)

## Set up rules for existing businesses

If you already have active members:

1. Log in to Stripe and go to *Payments → Rules.*
2. Enable the following 3D Secure rules:
   * Request 3DS if 3D Secure is required for card.
   * Request 3DS if 3D Secure is recommended for card.
3. Set up these custom Radar rules:
   * Block if `:cvc_check: in ('fail', 'unavailable', 'unchecked')` and `:authorized_charges_per_customer_all_time: = 0`
   * Block if `:address_zip_check: in ('fail', 'unavailable', 'unchecked')` and `:authorized_charges_per_customer_all_time: = 0`.
4. If you offer a free trial, enable *Use Radar on payment methods saved for future use.*

This costs 5¢ per attempt, but it helps prevent abuse and preserves a free trial experience. Alternative: Consider switching to a [paid trial model](/plans/individual-plans/create-a-plan/#enable-free-or-paid-trials) for added protection.

Need help setting up rules? [Contact Stripe support.](https://support.stripe.com/)

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