Countering Violent Extremism initiatives rest on the core assumption that it is possible to detect and stop violent extremists before they carry out attacks, through theories of radicalization which identify behaviors that are thought to be “indicators” or “risk factors.” This logic is the driving force behind the National Counterterrorism Center’s annual handbook for law enforcement agencies, which provides guidance for spotting these indicators - from legitimate calls to violence, to more troubling grey areas, such as “expressing frustration with employment situation.”