The Homeland Security Advisory System is a color-coded terrorism threat advisory scale. The different levels trigger specific actions by federal agencies and state and local governments, and they affect the level of security at some airports and other public facilities.
The scale consists of five color-coded threat levels, which are intended to reflect the probability of a terrorist attack and its potential gravity.
The specific government actions triggered by different threat levels include increasing police and other security presence at landmarks and other high-profile targets, more closely monitoring international borders and other points of entry, ensuring that emergency response personnel are ready, and, in some cases, deploying members of the National Guard and State Guard to assist local law enforcement on security details.
View the Citizen Guidance on the Homeland Security Advisory System document to learn about recommended actions for citizens during each stage of risk. This document is in PDF format and will require Arcobat Reader for viewing. Get Acrobat Reader.