&gt; Most large retailers only store the full credit card information for seconds while they process the transaction, when the transaction is complete it is discarded.<p>Couldn&#x27;t work around that by having some device that attaches to a randomly selected POS terminal, and then executes a series of dummy transactions using thousands of &quot;canary cards&quot; that were assigned to the store?<p>They could perhaps set this up with the credit cards companies so any use of the canary cards are automatically flagged when they&#x27;re used outside of the store that was issued them.