WooCommerce Card Testing Attacks: Why Failed Orders Signal Lasting Merchant Damage

When a WooCommerce store suddenly logs hundreds of failed orders, the cause is typically a card testing attack, where fraudsters use stolen credit card numbers to validate which cards are still active via the checkout page. The payment gateway itself is rarely at fault; bots systematically attempt low-value purchases across rotating IP addresses, sometimes reaching 100 checkouts per minute. The real harm extends well beyond the attack itself: elevated decline rates linger with card issuers, meaning legitimate customers face unexplained rejections weeks later. Successful fraudulent transactions generate chargebacks and fees that payment providers like PayPal may not refund, and sustained fraud ratios can trigger costly Visa and Mastercard merchant monitoring programs. Additionally, WooCommerce's automated failed-order emails sent to stolen or fake addresses inflate bounce rates, damaging the store domain's email sender reputation.