Is that how they did it !
And guess what ? They put one single lone guy to the task to track down the Bulgarians who did it.
Says it all while the NSA are concentrating on spying on their own population they leave the country exposed to cyber attacks and all that black hat firepower can't even thwart them. National security my ass. Cyber security is a national security risk obviously.
This is down to a few things.
Windows XP. POS systems connected to other windows systems on the network and not isolated. Surely there has to be a way to fully isolate everything and should never be connected to other windows machines on a LAN !