WASHINGTON — The campaign arm for House Republicans was hacked during the 2018 midterm campaign, a spokesman for the organization said on Tuesday.
The hack of the organization, the National Republican Congressional Committee, exposed thousands of sensitive emails from four senior aides for months. The breach, first reported by Politico, was detected in April by a vendor for the committee. It remains unclear who was behind the hack.
“The N.R.C.C. can confirm that it was the victim of a cyberintrusion by an unknown entity,” Ian Prior, a spokesman for the organization, said in a statement. “The cybersecurity of the committee’s data is paramount, and upon learning of the intrusion, the N.R.C.C. immediately launched an internal investigation and notified the F.B.I., which is now investigating the matter.”
Mr. Prior declined to comment further, citing the continuing investigation.
Senior House Republicans, including Speaker Paul D. Ryan of Wisconsin; Representative Kevin McCarthy of California, the House majority leader; and Representative Steve Scalise of Louisiana, the majority whip, were not aware of the breach until Politico reporters contacted them, a person familiar with the investigation said.
The person said that the techniques used by the hacker or hackers suggested that the breach was carried out by “a sophisticated actor.”
News of the breach came in the aftermath of a decisive Democratic victory in the House midterm elections, with Republicans losing 40 seats and Democrats winning control of the chamber.
Top national security leaders had warned before the November elections that Russia was engaged in a “pervasive” campaign to sow discord and influence American voters. And a once-bipartisan effort to pass legislation that would ensure that state officials could protect elections against hacking or influence failed before the bill even made it out of committee.
The special counsel, Robert S. Mueller III, is investigating foreign interference in the 2016 presidential election, and is delving into the hacking attacks against Hillary Clinton’s presidential campaign, the Democratic National Committee and the Democratic Congressional Campaign Committee.