A number of House Republicans’ campaign aides were hacked during this years’ midterms, according to a report first published Tuesday by Politico.

Four senior aides of the National Republican Congressional Committee had their emails hacked, and this went on for several months, according to the report. An NRCC vendor spotted an attack in April, and subsequently told the committee as well as a cybersecurity contractor. The FBI was also informed about the matter.

“The NRCC can confirm that it was the victim of a cyber intrusion by an unknown entity,” said Ian Prior of Mercury Public Affairs, a public relations agency hired by the committee. “Upon learning of the intrusion, the NRCC immediately launched an internal investigation and notified the FBI, which is now investigating the matter.”

According to Politico, congressional Republicans were kept in the dark about the intrusion to avoid compromising the investigation. At the moment it’s not known who was behind the breach, although it’s said that because of the nature of the attack, party officials believe a foreign government could have been the culprit.

“We don’t want to get into details about what was taken because it’s an ongoing investigation,” a senior party official said. “Let’s say they had access to four active accounts. I think you can draw from that.”

A former Justice Department official and NRCC operative told Politico he could not speak about the hack because it might jeopardize the investigation, while the FBI said it would not comment regarding its ongoing investigation.

What we do know is that of the thousands of emails that were seen, none have surfaced online, a party official said. The emails were not used in an attempt to threaten those involved with the release of information.

“Although we do not yet know how long the attackers had access to the accounts or who exactly is behind this breach, it was undoubtedly mounted by advanced threat actors,” Justin Fier, director for cyber intelligence and analytics for the cybersecurity firm Darktrace, said in an email to SiliconANGLE. “It is not uncommon for persistent adversaries to spend months, and sometimes years, in a network searching for valuable data or slowly exfiltrating sensitive information. These ‘low and slow’ attacks are the new reality for both political organizations and corporations alike, and all entities need to be prepared to defend themselves from a new era of threat and level of attacker.”

The hack could be compared to what happened to the Democratic National Committee in 2016 when its database was breached during the presidential election. This was a matter of embarrassment for the DNC.

“The DNC should be ashamed of themselves for allowing themselves to be hacked. They had bad defenses, and they were able to be hacked,” Donald Trump said in the “Face the Nation” interview for CBS News in July. “I heard they were trying to hack the Republicans, too. But, and this may be wrong, but they had much stronger defenses.”

Or maybe not.

Image: Elliott P./Flickr