The National Republican Congressional Committee was hacked during the 2018 US midterm elections.
The breach, first reported by Politico, exposed thousands of emails to an unknown hacker.
"The NRCC can confirm that it was the victim of a cyber intrusion by an unknown entity," Ian Prior, a spokesman for the NRCC, said in a statement. "The cybersecurity of the Committee's data is paramount, and upon learning of the intrusion, the NRCC immediately launched an internal investigation and notified the FBI, which is now investigating the matter."
The FBI declined to comment.
The NRCC also reported the hack to CrowdStrike, the cybersecurity company that led the investigation on the.
CrowdStrike acknowledged the NRCC had asked it to investigate "unauthorized access" to the committee's emails in April. The company had previously helped protect the NRCC's internal corporate network, which wasn't affected.
None of the hacked emails were published, and the attackers didn't contact the NRCC with threats to post them online, according to Politico.
Political organizations and campaigns were on high alert for cyberattacks after a major hack of the DNC in 2016. The Justice Department charged. They infiltrated the Democrats' email servers and published private messages online.
That included 50,000 emails from John Podesta, who was presidential candidate Hillary Clinton's campaign manager at the time.
Politically motivated hackers made several attempts during the 2018 elections to access candidates' emails. Then-Sen. Claire McCaskill, a Democrat from Missouri who was running for re-election, noted that a .
In attempts to prevent these cyberattacks, companies likedesigned to fool campaign staffers. Google also offered to politicians' emails, through security keys and two-factor authentication.
The NRCC didn't comment on how it was breached or why it waited until after Election Day to disclose the hack.
"To protect the integrity of that investigation, the NRCC will offer no further comment on the incident," Prior said.
Originally published at 10:23 a.m. PT.
Updated at 11:11 a.m.: To note that the FBI declined to comment.
Updated at 5:38 p.m.: Adds CrowdStrike comment.
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