Utilize your financial knowledge, give your answer or opinion to the input question or subject . Answer format is not limited.

MasterCard won't disclose who leaked my credit card details
File a John Doe lawsuit, "plaintiff to be determined", and then subpoena the relevant information from Mastercard.  John Doe doesn't countersue, so you're pretty safe doing this.  But it probably won't work.  Mastercard would quash your subpoena.  They will claim that you lack standing to sue anyone because you did not take a loss (which is a fair point).    They are after the people doing the hacking, and the security gaps which make the hacking possible.  And how those gaps arise among businesses just trying to do their best.  It's a hard problem.  And I've done the abuse wars professionally.  OpSec is a big deal.  You simply cannot reveal your methods or even much of your findings, because that will expose too much of your detection method.  The ugly fact is, the bad guys are not that far from winning, and catching them depends on them unwisely using the same known techniques over and over.  When you get a truly novel technique, it costs a fortune in engineering time to unravel what they did and build defenses against it.  If maybe 1% of attacks are this, it is manageable, but if it were 10%, you simply cannot staff an enforcement arm big enough - the trained staff don't exist to hire (unless you steal them from Visa, Amex, etc.)  So as much as you'd like to tell the public, believe me, I'd like to get some credit for what I've done -- they just can't say much or they educate the bad guys, and then have a much tougher problem later.  Sorry!  I know how frustrating it is! The credit card companies hammered out PCI-DSS (Payment Card Industry Data Security Standards).  This is a basic set of security rules and practices which should make hacking unlikely.  Compliance is achievable (not easy), and if you do it, you're off the hook.  That is one way Amy can be entirely not at fault.  Example deleted for length, but as a small business, you just can't be a PCI security expert.  You rely on the commitments of others to do a good job, like your bank and merchant account salesman.  There are so many ways this can go wrong that just aren't your fault.   As to the notion of saying "it affected Amy's customers but it was Doofus the contractor's fault", that doesn't work, the Internet lynch mob won't hear the details and will kill Amy's business. Then she's suing Mastercard for false light, a type of defamtion there the facts are true but are framed falsely.   And defamation has much more serious consequences in Europe.  Anyway, even a business not at fault has to pay for a PCI-DSS audit.  A business at fault has lots more problems, at the very least paying $50-90 per customer to replace their cards.  The simple fact is 80% of businesses in this situation go bankrupt at this point.   Usually fraudsters make automated attacks using scripts they got from others.  Only a few dozen attacks (on sites) succeed, and then they use other scripts to intercept payment data, which is all they want. They are cookie cutter scripts, and aren't customized for each site, and can't go after whatever personal data is particular to that site. So in most cases all they get is payment data. It's also likely that primary data, like a cloud drive, photo collection or medical records, are kept in completely separate systems with separate security, unlikely to hack both at once even if the hacker is willing to put lots and lots of engineering effort into it.  Most hackers are script kiddies, able to run scripts others provided but unable to hack on their own.   So it's likely that "none was leaked" is the reason they didn't give notification of private information leakage.  Lastly, they can't get what you didn't upload.  Site hacking is a well known phenomenon.  A person who is concerned with privacy is cautious to not put things online that are too risky.  It's also possible that this is blind guesswork on the part of Visa/MC, and they haven't positively identified any particular merchant, but are replacing your cards out of an abundance of caution.