I haven't done any extensive reading or research. What I know I just picked up following anti-racists and anti-fascists online. I can't stress enough how much effort anti-racists and anti-fascists put into try to alert the public to what goes on, the public just ignores them.
I know that Talia Lavin just published a book called Culture Warlords where she details infiltrating white supremacist groups online. This book was published last October, so her evidence is maybe 1 to 2 years older than that.
From Aug 2017, Propublica, Documenting Hate, He Spent Years Infiltrating White Supremacist Groups. Here’s What He Has to Say About What’s Going on Now. There are plenty of accounts of people infiltrating white supremacist groups.
One story that blew up last year was about a member of a white supremacist hate group got pissed (I vaguely remember he felt like he was being edged out of the group he help found), so he downloaded all of the ransom videos from their group folder and uploaded them all to a public space.
The Alt-Right Playbook is an attempt to break apart and explain the tactics right wing extremists use to recruit, use to spread their ideas, use to deflect criticism, etc. It also talks about why conservatives allow them space.
Those are the ones that pop into my head right now.