Approximately four million former and current federal employees may have had personally identifiable information stolen as part of a massive cyber theft announced by the administration Thursday.
The Office of Personnel Management, the federal government's human resources office, is warning employees who may be affected to be on the lookout for financial fraud. The office, which handles security clearances and other sensitive information, said it identified that its systems had been breached in April.
"Protecting our federal employee data from malicious cyber incidents is of the highest priority at OPM," Katherine Archuleta, the office's director, said in a statement.
The office said it upgraded security on its servers after the breach, instating anti-malware software on its systems and reviewing connections to make sure "only legitimate business connections have access to the internet."
In a statement, the FBI said it is investigating the breach and vowed to "hold accountable those who pose a threat in cyberspace."
According to reports in the Washington Post and Wall Street Journal, federal authorities believe China to be the culprit, marking the second time over the past year that the country has succeeded in penetrating the federal government's cyberdefenses. Both China and Russia constantly wage cyberattacks on the U.S.