Stripe Radar with tight custom rules is the first pick for shutting down card testing, since it scores every payment intent before authorization and can block a whole attack pattern with one rule. Edge rate limiting, a checkout CAPTCHA, and 3-D Secure are the strongest backups when Radar by itself leaves gaps.
compare stripe card testing attack
Card testing is a volume game. An attacker needs thousands of attempts to find a live number, so every layer that raises the cost per attempt shrinks the attack.
compare stripe card testing attack
What does a card testing attack look like on Stripe?
Attackers script small charges, often $0.50 to $1, across many card numbers and email addresses to learn which ones authorize. Numbers that work get reused for larger purchases or resold. The fingerprints show up as spikes in declines, mismatched country pairs between card and IP, and repeated card fingerprints from a narrow IP range.
Longtail Stripe Card Testing Attack Guide
How do the five main options compare?
- Stripe Radar custom rules. Best first move. Block on card fingerprint velocity, country mismatch, and repeated decline codes. Included with standard Stripe processing.
- Edge rate limiting and bot management. Stops traffic before it reaches checkout. Strong against crude scripts, weaker against distributed residential proxy pools.
- Checkout CAPTCHA. Cheap and fast to deploy. Adds friction for every buyer, so trigger it on risk signals only.
- 3-D Secure. Moves liability and blocks stolen numbers at the issuer. Completion rates fall, so apply it selectively.
- Third-party fraud engines. Best for high volume merchants with a data team. Overlaps heavily with Radar, so audit both before paying twice.
Why is rate limiting alone not enough?
Distributed attacks spread attempts across thousands of IPs, so per-IP caps miss most of the traffic. Pair limits with device fingerprinting and account-level velocity checks. A rule that caps attempts per card fingerprint catches what IP throttling cannot.
When does 3-D Secure pay off?
Use it on first-time buyers, high-value baskets, and any session Radar flags as elevated risk. It turns a silent authorization into an issuer challenge, which stops most stolen numbers. Keep it off for returning customers to protect conversion.
How do you know the defense worked?
Track the ratio of declined to successful charges, distinct cards per IP, and dispute rate week over week. A working defense cuts authorization attempts sharply while leaving legitimate conversion flat. If conversion drops along with attack volume, the rules are too broad.