Checkout Firewall
Ask Shopify to reject card-testing checkouts
High-confidence matches return a checkout validation error. New installs start in Monitor, so buyers are not rejected on day one.
Built into Shopify checkout
Card testers retry stolen cards until one is accepted. Checkout Firewall asks Shopify to reject the matching checkout. A wallet can still open unless Shopify refuses that payment method.
Checkout Validation Function
Rules compile in our backend and sync into Shopify. Checkout never calls an external fraud API and never sees card numbers.
Shop-local lists first
Blacklist a phone or address for this store. Shared network hashes need multiple independent shops and a high-confidence score.
Explainable decisions
Activity shows would-block rows in Monitor, without exposing another store’s customers.
Protection modes
Pick how hard the Function should act. You can change mode anytime in Settings.
- MonitorLog would-blocks. Never stop checkout. Default for new installs.
- BalancedBlock high-confidence matches at checkout.
- AggressiveStricter thresholds for shops under active attack.
Install from the Shopify App Store
Install Checkout Firewall from the App Store, then stay in Monitor until Activity looks right. Switch to Balanced when you are ready to block.
This app is not
A generic fraud suite, IP blocker, chargeback manager, Stripe Radar replacement, or “AI fraud detection.” It is a checkout firewall for card-testing.