The Wall Street Journal reports that the news came to light when Visa withdrew from using the company's services as a result of the problem. Though card and account information was exported from the the servers of Global Payment, it's currently thought that the criminals didn't obtain card-holder names, addresses or Social Security numbers.
A spokesperson from Global Payments told the Wall Street Journal that "[b]ased on the forensic analysis to date, network monitoring and additional security measures, the company believes that this incident is contained."
The move by Visa to stop using the services of Global Payment is a big one: it's a rare occurrence in the industry, so signals a complete lack of trust. It's not yet clear whether others will follow suit. As of Friday, banks were taking extra care to monitor accounts for suspicious activity. [Wall Street Journal]