The Department of Homeland Security recently issued a chilling report: Americans, it said, can expect an upsurge in "rightwing extremism" from White nationalists, militias, and groups like the Ku Klux Klan. The Klan, of course, has had a hand in some of the nation's most infamous acts of racial terror and murder. But what does the KKK look like today? Photographer Anthony Karen has documented the modern-day Klan in their homes, at rallies, and at Klan gatherings, taking us deep inside a world we would otherwise never see -- a world most of us might not even want to know about. The unnerving photos featured here, exclusively on LIFE.com, are from his new book, "The Invisible Empire: Ku Klux Klan." "The majority of people I've come across," Karen told LIFE, "you'd only know they were in the Klan if they decided to share that."