Credit card holders should carefully check statements and if directly notified of breach, they should change their account information.  FBI notes these sophisticated attacks most likely impacted more than 3 major retailers.

QUOTE: Target hack likely to just be the beginning. The FBI has warned US retailers to prepare for more cyber attacks after discovering about 20 hacking cases in the past year that involved the same kind of malicious software used against Target in the holiday shopping season. The US Federal Bureau of Investigation distributed a confidential, three-page report to retail companies last week describing the risks posed by “memory-parsing” malware that infects point-of-sale (POS) systems, which include cash registers and credit-card swiping machines found in store checkout aisles.