A new doc for the intel library from the National Counter-terrorism Center.

This handbook lists what to look for (indicators) that may foreshadow a violent terrorist action.

An Excerpt:

The indicators of violent extremist mobilization described herein are intended to
provide federal, state, local, territorial and tribal law enforcement a roadmap of observable
behaviors that could inform whether individuals or groups are preparing to engage in
violent extremist activities including potential travel overseas to join a Foreign Terrorist
Organization (FTO). The indicators are grouped by their assessed levels of diagnosticity—
meaning how clearly we judge the behavior demonstrates an individual’s trajectory towards
terrorist activity. The list also includes additional information concerning what the behavior
could indicate, identifies likely observers, and provides a probable timeframe between
behavior and an ultimate violent act. Some of these activities might be constitutionally
protected and may be insignificant on their own, but, when observed in combination
with other suspicious behaviors, may constitute a basis for reporting. Law enforcement
(LE) action should not be taken based solely on the exercise of constitutionally protected
activities or on the apparent race, ethnicity, national origin, or religion of the subject.