MAK: All three of those arrested by federal law enforcement were members of a Boogaloo Facebook group, according to a criminal complaint. NPR examined the Facebook profile of one of the suspects and found that he was a member of multiple Facebook groups relating to the Boogaloo movement. Joel Finkelstein is the director of the Network Contagion Research Institute, which tracks hateful ideology online. He says that Facebook has become a key place for members of the Boogaloo movement to organize, recruit and discuss communication strategies through the use of private groups.

JOEL FINKELSTEIN: In terms of a structure that allows these things to remain hidden, I think it goes without saying, almost, that Facebook is far and away one of the best kinds of platforms that you could have for that purpose.

MAK: Finkelstein said that as he and his team researched these extremist groups, Facebook began to advertise to him.

FINKELSTEIN: We were given targeted advertisements by the platform supporting the Boogaloo in the form of shirts containing Boogaloo memes, hats, military badges containing this kind of material.

— from Tim Mak's report, “Facebook Becomes Key Place For Extremist Boogaloo Movement Organizers,” on NPR's “Weekend Edition” last Saturday.