Could very well work, only you would need cooperation with one or more major payment processors/card issuers. The way it would work is that shops are given hob

Could very well work, only you would need cooperation with one or more major payment processors/card issuers. The way it would work is that shops are given hobeypot cards and asked to use them weekly for dummy payments. The moment one of these cards show up anywhere else than the shop it was sent to you can expect the shop has been hacked. It is not failsafe and you will have to wait until a batch with this card is stolen before this tells you where.