The National Republican Congressional Committee, the Republican Party's campaigning arm, has confirmed it has fallen victim to a major compromise of its email system.
Following an early report from Politico, the committee confirmed to multiple outlets that someone had been surveilling its messages for months.
The NRCC did not respond to a Register request for comment.
The breach is said to have been found by a security vendor working with the NRCC back in April.
The intruder reportedly had access to the email accounts of at least four NRCC aides and, by the time the breach was discovered, had likely been collecting thousands of sent and received emails over the course of several months.
According to Politico's account of the matter, much of the GOP leadership, including Speaker Paul Ryan (R-WI) and Majority Leader Kevin McCarthy (R-CA) was left in the dark about the matter as the NRCC sought to investigate the breach on its own.