Card Testing Attacks: Why They Target Your Stripe Checkout First

Card testing is one of the most frustrating experiences for businesses using Stripe. You wake up to a burst of small transactions, strange customer names, and error‑filled logs—and then, weeks later, chargebacks and disputes start to roll in. It feels random from the inside, but from the attacker’s point of view, your checkout is just a tool.Criminals buy or steal huge lists of card numbers. Most of those cards are dead: cancelled, expired, or flagged. To find the ones that still work, they need a live payment system to test against. Stripe checkouts, storefronts, and low‑friction payment links are perfect for this: always online, globally accessible, and often lightly protected.These attacks often start small. A wave of low‑value attempts (sometimes just authorization holds) probes your system. If your store doesn’t have proper velocity limits, rule‑based screening, and verification in place, attackers can send thousands of tests through before anything looks suspicious. Successful tests become “good” cards—used later for bigger purchases, or resold to others who will hit you and other merchants with fraud and chargebacks.You can’t stop card testing by hoping it goes away. You stop it by making your Stripe environment a terrible place to run tests. That means tightening rules around repeated failures, adding friction for obviously automated behaviour, and treating sudden bursts of small transactions as a serious signal—not a minor annoyance. Combined with smart dispute handling, this turns you from an easy testing ground into a high‑risk, low‑reward target.At CyberVeil, we focus on these quiet attack patterns. When we design rules, flows, and verification for your Stripe store or marketplace, card testing is one of the first threat models we test against—because if you can resist card testers, you’re already ahead of most of the internet.