Donna Brazile says in her new book the Democratic National Committee (DNC) went against professional advice and sat idly for a month while Russians stole data because primaries were still underway in a number of states.

"In May, when CrowdStrike recommended that we take down our system and rebuild it, the DNC told them to wait a month, because the state primaries for the presidential election were still underway, and the party and the staff needed to be at their computers to manage these efforts," Brazile wrote in her new book, "Hacks."

"For a whole month, CrowdStrike watched Cozy Bear and Fancy Bear operating. Cozy Bear was the hacking force that had been in the DNC system for nearly a year."

Cozy Bear and Fancy Bear are cybersecurity firms that have reported ties with Russian hackers. Both groups are blamed for the hacks on the DNC in 2016. CrowdStrike is a private U.S. cybersecurity firm that oversaw the protection of the DNC's servers.