In 2377 Voyager helped a group of Borg drones who kept their individuality in a hidden virtual world, Unimatrix Zero, to resist the Borg Queen.
Some drones had a rare mutation that let them visit Unimatrix Zero, a virtual world where they lived as individuals while regenerating, though they forgot it when they woke. Seven of Nine had once been one of them. The Borg Queen discovered the place and began destroying drones who went there.
Janeway, Tuvok and B'Elanna Torres allowed themselves to be assimilated while protected by a neural suppressant. They released a nanovirus so these drones would keep their memories when awake. The Queen destroyed several cubes to stop them, but drones such as Korok began a resistance within the Collective.