A massive data breach at the Office of Personnel Management first discovered in April actually happened months earlier, according to OPM.
The only reason the agency was even able to detect the intrusion took place was because OPM had upgraded its cybersecurity detection and monitoring tools, OPM press secretary Samuel Schumach said in a statement.
"Within the last year, OPM has undertaken an aggressive effort to update its cybersecurity posture, adding numerous tools and capabilities to its various networks," Schumach said.
As many as 4 million current and former federal employees may have had their personally identifiable information compromised in a breach of IT systems at the agency. OPM detected the data breach in April and learned sensitive information may have been taken in May, but waited until June 4 to announce it publicly.
See also: OPM hack could affect 4 million people
See also: Lawmakers fault OPM over massive cyber breach
White House Press Secretary Josh Earnest said in a briefing June 5 said agencies were constantly updating and reviewing their security measures to keep up with "persistent foes" in the cyber world.
"We have seen our adversaries use innovative techniques and to learn from their previous efforts to find vulnerabilities in our systems and exploit them," Earnest said. "The administration takes very seriously the need to mitigate those kinds of intrusions if and when they are detected on the network. "
He said federal employees will begin receiving notifications June 8 if their data was compromised, and that the federal government will be as open about the attacks as possible without compromising cybersecurity tools and procedures.
"The federal government has an obligation to communicate directly and promptly in as much detail as possible with those who may be personally affected by these incidents," Earnest said.
