Terror alert systems are standardised

emergency population warning An emergency population warning is a method whereby local, regional, or national authorities can contact members of the public en masse to warn them of an impending emergency. These warnings may be necessary for a number of reasons, including: * ...

systems for describing and disseminating information about

terrorism Terrorism, in its broadest sense, is the use of criminal violence to provoke a state of terror or fear, mostly with the intention to achieve political or religious aims. The term is used in this regard primarily to refer to intentional violen ...

-related threats. They became more popular after the

September 11 attacks The September 11 attacks, commonly known as 9/11, were four coordinated suicide terrorist attacks carried out by al-Qaeda against the United States on Tuesday, September 11, 2001. That morning, nineteen terrorists hijacked four commercia ...

on the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

in 2001.

Australia

National Counter-Terrorism Alert Level * Certain - terrorist attack is imminent or has occurred * Expected- terrorist attack is highly likely * Probable - terrorist attack is likely * Possible - terrorist attack could occur * Low - terrorist attack is not expected Administered by the Federal Attorney-General's Department.

France

Plan Vigipirate * Yellow - to stress vigilance * Orange - to warn of terrorist action * Red - to warn of serious attempts * Crimson - to warn of major attempts

Ireland (Republic of)

International Terror Threat Level * Low: An attack is deemed unlikely. * Moderate: An attack is possible, but not likely. * Substantial: An attack is a strong possibility. * Severe: An attack is highly likely. * Critical: An attack is imminent or has occurred. Administered by the

Garda Síochána (; meaning "the Guardian(s) of the Peace"), more commonly referred to as the Gardaí (; "Guardians") or "the Guards", is the national police service of Ireland. The service is headed by the Garda Commissioner who is appointed by the Irish Gover ...

. Since November 2015, the international terrorism threat level is considered to be at moderate, meaning an attack is "possible but not likely".

Netherlands

Russia

* Blue - an unconfirmed information about real terroristic threatУРОВНИ ТЕРРОРИСТИЧЕСКОЙ ОПАСНОСТИ , Национальный антитеррористический комитет
/ref> * Yellow - a confirmed information about real terroristic threat * Red - an information about committed terrorist act

United Kingdom

* Low - an attack is unlikely * Moderate - an attack is possible, but not likely * Substantial - an attack is a strong possibility * Severe - an attack is highly likely * Critical - an attack is expected imminently or has occurred Administered by the Joint Terrorist Analysis Centre

United States

Homeland Security Advisory System * Low - Low risk of terrorist attacks * Guarded - General risk of terrorist attacks * Elevated - Significant risk of terrorist attacks * High - High risk of terrorist attacks * Severe - Severe risk of terrorist attacks Administered by the

Department of Homeland Security The United States Department of Homeland Security (DHS) is the U.S. federal executive department responsible for public security, roughly comparable to the interior or home ministries of other countries. Its stated missions involve anti-terr ...

National Terrorism Advisory System The National Terrorism Advisory System (NTAS) is a terrorism threat advisory scale used by the US Department of Homeland Security since April 26, 2011. The NTAS is the replacement for the often-criticized, color-coded Homeland Security Advisor ...

* Elevated Threat - Significant or high risk of terrorist attacks * Imminent Threat - Critical risk of terrorist attacks

References

Alert measurement systems {{Government-stub