It has been reported that hackers working for the "Chinese state" have breached the information systems at the Office of Personnel Management (OPM) in December 2014, putting up to 4?million current and former federal employees' personal data at risk.
It is alleged that this hack represents the "second major intrusion into the same system by China", and sources report that this is the second significant breach into the US government's networks in the past year (with Russian hackers compromising the White House e-mail systems prior to this intrusion).
The OPM are now in the process of better protecting its data storage, including the introduction of data masking and redaction. The Director of the OPM, Katherine Archuleta, stated that "We’ve purchased tools to be able to implement that capability for all [the data]".
For more information, please see the OPM website here.