How to Identify Card TestingHow to Detect Card Cracking & Testing Fraud Before It’s Too Late

Shelley Palmer | August 28, 2025 | 2 min read

Spotting the Red Flags Before the Alarm Bells Ring

How do you know when you’ve been targeted by a card tester?

By the time you get a notification from your payment processor, it’s already too late. The attack is well underway, and you’ve probably already lost thousands.

There’s one piece of good news, though: while fast, card testing bots are fairly clumsy and easy to spot. For example, a sudden spike in transaction declines, a flurry of small orders, or payments with CVV and AVS mismatches are all red flags for card testing.

In this chapter, we highlight several telltale signs of a card testing attack so you know what to look out for.

Card Testing

Criminals validate stolen credit card information by making small, inconspicuous purchases. Once they confirm the card details are valid, they may proceed to make larger unauthorized transactions. This tactic helps fraudsters avoid detection until they have successfully exploited the stolen card.

Knowledge Guide

How Will I Know if I’ve Been Targeted in a Card Testing Attack?

There’s a good chance that your business has already been the victim of card testing scams in the past. Either way, you want to make sure you’re doing everything you can to keep it from happening. The key is knowing what to look for.

There are several signs which may indicate that card testers have targeted your business, including:

Increased Declines

A sudden spike in declined transactions can indicate that bots are attempting to use stolen or invalid card information at your business.

Multiple Small Transactions

If you notice a bunch of small transactions coming from the same card or IP address, it could be a sign that someone is testing the card.

Transaction Velocity

Watch for customers making an unusual number of transactions in a short amount of time, using multiple different cards. This may indicate that the customer is attempting to test multiple cards at once.

Mismatched Card Credentials

Don’t accept payments with addresses that don’t match up to historical data or display other suspicious behaviors. For example, if the billing address for the card does not match the customer's location.

Put card fraud to the test.

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If you suspect that card testers have targeted your business, it's important to take steps to protect your business's financial security. This may include reporting the incident to the card issuer and law enforcement, as well as reviewing and updating your business's security and fraud prevention procedures.

Card Testing

How to Identify Card TestingHow to Detect Card Cracking & Testing Fraud Before It’s Too Late