The House Republican fundraising committee suffered an email hack during the run-up to the 2018 congressional midterm elections.
The National Republican Congressional Committee discovered in April that there were multiple intrusions over the course of a few months into email accounts of four of its top officials, according to a source with direct knowledge of the matter. It's unclear who was behind the hack.
GOP leadership, including the likes of House Speaker Paul Ryan, R-Wis., House Majority Whip Steve Scalise, R-La., and House Majority Leader Kevin McCarthy, R-Calif., were not made aware of what took place at the NRCC until Monday, this source said.
The NRCC responded with an investigation of its own and contacted the FBI, which is continuing to look into the attack. Politico first reported on the hack earlier Tuesday.
"The NRCC can confirm that it was the victim of a cyber intrusion by an unknown entity," Ian Prior, a spokesman for the NRCC and an executive at Mercury Public Affairs, told CNBC in a statement. "The cyber security 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," he added.
Leadership at the NRCC hired top law firm Covington & Burling as its legal counsel after the hack. According to Federal Election Commission records, the NRCC paid the law firm more than $250,000 for legal consulting from July through September.
The intrusion came as Republicans and their party committees, such as the NRCC, were trying to maintain their majority in the U.S. House of Representatives in the buildup to the November elections. Democrats won a majority in the House, and are projected to gain at least 39 seats, while Republicans will expand their majority in the Senate, adding two seats.
The NRCC was also outraised by its opponents, the Democratic Congressional Campaign Committee, throughout the 2018 election cycle. The DCCC brought in $250 million, compared with the NRCC's $174 million, according to the nonpartisan Center for Responsive Politics.
Sen. Mark Warner, the ranking Democratic member of the Senate Intelligence Committee, responded to the news of the hack in a tweet on Tuesday.