Mike Murray, Lookout's VP of security intelligence, told CNN that the fake page and the real one looked remarkably similar. "It was very convincing," he said. He added that it was possible the fake page was sent to Democrats through email in an attempt to gather Votebuilder login information.

The DNC was the victim of a hack in 2016, which led to the public release of thousands of internal emails. Ever since, the party has been working to strengthen its security efforts. It hired former Yahoo security chief Bob Lord earlier this year and ex-Twitter VP Raffi Krikorian as its chief technology officer in 2017.

This isn't the first cyberattack to be uncovered ahead of the 2018 midterm elections. Senator Bill Nelson (D-FL) announced earlier this month that Russian operatives had "penetrated" Florida election systems and a number of phishing attacks targeting 2018 campaigns have been thwarted in recent months.

"These threats are serious and that's why it's critical that we all work together, but we can't do this alone," Lord said to CNN. "We need the [Trump] administration to take more aggressive steps to protect our voting systems. It is their responsibility to protect our democracy from these types of attacks."

A source told CNN that the DNC doesn't believe the database was accessed or altered. "While it's clear that the actors were going after the party's most sensitive information -- the voter file -- the DNC was able to prevent a hack by working with the cyber ecosystem to identify it and take steps to stop it," Lord told NPR.