How to Stop Card Testing Attacks on Shopify

Card testing is high-velocity stolen-card checks at checkout. FraudPulse classifies that pattern in your chargeback/auth history and ranks specific Shopify Protect (and Radar, if you use Stripe) rule changes, each with estimated fraud-capture and false-positive percentages, so you can block testers without locking out real buyers - alongside Protect, not instead of it.

Testers hammer checkout with many cards in a short window, often low value, looking for live PANs. Panic responses - blocking all international cards, or flipping every control to maximum - can stop the attack and also wipe conversion. The durable fix is velocity and rule changes matched to your auth and dispute patterns.

What to do when card testing hits my checkout

In the first hour: check Shopify and Stripe fraud views, tighten obvious velocity and CVC-related controls carefully, and avoid nuking entire regions without a false-positive estimate. Then use classified history to rank durable Protect (and Radar) changes so you are not stuck in emergency mode.

• Confirm it is testing (velocity, auth failures, repeated BIN/email patterns) vs a one-off fraud spike.
• Keep Shopify Protect on - it is enforcement; you still need the right settings for your mix.
• Prefer targeted velocity and signal rules over blanket declines.
• Watch false positives: every FraudPulse recommendation includes an estimated false-positive percentage.

Stripe Radar velocity rules (if checkout runs on Stripe)

When Shopify checkout is paid through Stripe, Radar velocity rules are often the right lever for testing: repeated attempts, card/email/IP clustering, and short-window thresholds. FraudPulse can rank specific Radar changes alongside Protect recommendations when both are connected - still advisory, not a Radar replacement.

You do not always need Signifyd or another full platform immediately. If Protect and Radar are already on, start by changing the rules that match your testing pattern. Platforms remain a separate buy when you want a guarantee stack.

See also how to reduce chargebacks on Shopify, how it works, pricing, and the FAQ.

Need ranked rules for a live testing wave? Book a Demo.