Krebsonsecurity has the story
It happened on March 2014. After the card information is harvested, they are then sold on the hacker’s black market.
It is here where the breach was found. It is not known where it happened, and how many cards were affected.
The hackers black market is not that informative.
Again we must ask you to test your computer systems, because the solution is not to go back to the 70’s:
Where the credit card slip is kept and the card will hopefully be valid.