White supremacists and other domestic extremists maintain an active presence in U.S. police departments and other law enforcement agencies. [FBI] policies have been crafted to take this infiltration into account. An October 2006 FBI internal intelligence assessment ... raised the alarm over white supremacist groups' "historical" interest in "infiltrating law enforcement communities or recruiting law enforcement personnel." In 2009 ... a Department of Homeland Security intelligence study, written in coordination with the FBI, warned of the "resurgence" of right-wing extremism. The report concluded that "lone wolves and small terrorist cells embracing violent right-wing extremist ideology are the most dangerous domestic terrorism threat in the United States." The report caused an uproar. Faced with mounting criticism, DHS Secretary Janet Napolitano disavowed the document. The agency's unit investigating right-wing extremism was largely dismantled and the report's lead investigator was pushed out. "They stopped doing intel on that, and that was that," Heidi Beirich, who leads the Southern Poverty Law Center's tracking of extremist groups, told The Intercept. Daryl Johnson, who was the lead researcher on the DHS report ... says the problem has since gotten "a lot more troublesome." Homeland Security has given up tracking right-wing domestic extremists. "It's only the FBI now," he said, adding that local police departments don't seem to be doing anything to address the problem.