National Terrorism Advisory System

This document describes the National Terrorism Advisory System (NTAS), which replaced the color-coded Homeland Security Advisory System. NTAS is designed to communicate information about terrorist threats to the public, government agencies, first responders, transportation hubs, and the private sector. The system uses "Imminent Threat" and "Elevated Threat" alerts, each with a specific expiration date. The public is encouraged to report suspicious activity to local law enforcement or call 911.