Terror alert system
Terror alert systems are standardized frameworks employed by governments to communicate the assessed likelihood and potential severity of terrorist threats, enabling authorities, organizations, and the public to take appropriate preventive measures. These systems typically employ tiered threat levels, ranging from low to critical, and are designed to reflect each country’s specific security context, intelligence assessments, and risk management strategies. They provide guidance on protective measures, situational awareness, and coordinated responses across federal, regional, and local agencies.
Terror alert systems are an integral part of national security strategies, aiming to enhance public safety through timely communication, clear guidance, and preparedness planning. Examples include the United States’ National Terrorism Advisory System, the former Homeland Security Advisory System, the United Kingdom’s UK Threat Levels, Canada’s National Terrorism Threat Level, and the Netherlands' Counterterrorism Alert System and Terrorist Threat Assessment Netherlands.
Australia
National Counter-Terrorism Alert LevelCertain - terrorist attack is imminent or has occurredExpected- terrorist attack is highly likelyProbable - terrorist attack is likelyPossible - terrorist attack could occurLow - terrorist attack is not expectedAdministered by the Federal Attorney-General's Department.
Canada
Canada's National Terrorism Threat Level is a federal tool indicating the likelihood of a violent terrorist act occurring in Canada. It is assessed by the Integrated Terrorism Assessment Centre and approved by the Director of the Canadian Security Intelligence Service. ITAC considers classified intelligence and open-source intelligence on the intentions, capabilities, and opportunities of terrorist actors when making its assessment. Its purpose is to ensure a shared understanding of national risk and to guide appropriate responses across government and law enforcement. When the threat level rises to High or Critical, the Federal Terrorism Response Plan may be activated, coordinating emergency measures across federal, provincial, and territorial authorities.National Terrorism Threat LevelVery low - A violent act of terrorism is highly unlikely. Measures are in place to keep Canadians safe.Low - A violent act of terrorism is possible but unlikely. Measures are in place to keep Canadians safe.Medium - A violent act of terrorism could occur. Additional measures are in place to keep Canadians safe.High - A violent act of terrorism is likely. Heightened measures are in place; Canadians are informed what actions to take.Critical - A violent act of terrorism is highly likely and could occur imminently. Exceptional measures are in place; Canadians are informed what actions to take.
Canada's current level is Medium, a level that has been in effect since October 2014. Threat levels are assessed at a minimum of every four months, or more frequently as required.
France
Plan VigipirateYellow - to stress vigilanceOrange - to warn of terrorist actionRed - to warn of serious attemptsCrimson - to warn of major attemptsIreland (Republic of)
International Terror Threat LevelLow: 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.
Since November 2015, the international terrorism threat level is considered to be at moderate, meaning an attack is "possible but not likely".
Russia
Blue - an unconfirmed information about real terroristic threatYellow - a confirmed information about real terroristic threatRed - an information about committed terrorist actUnited Kingdom
The United Kingdom’s terrorism threat level system is maintained by MI5 and the Joint Terrorism Analysis Centre to communicate the likelihood of a terrorist attack. It categorizes threats into five levels: Low, Moderate, Substantial, Severe, and Critical, reflecting increasing probability of an attack. These levels are determined through intelligence assessments and are intended to guide protective security measures across government, businesses, and public sectors. Changes to the threat level are publicly announced to inform the public while ensuring appropriate security measures are implemented nationwide.Terrorism Threat LevelsLOW - an attack is unlikelyMODERATE - an attack is possible, but not likelySUBSTANTIAL - an attack is likelySEVERE - an attack is highly likelyCRITICAL - an attack is highly likely in the near future
The UK's current level is SUBSTANTIAL, while Northern Ireland's current level is SUBSTANTIAL.
United States
Homeland Security Advisory SystemLow - Low risk of terrorist attacksGuarded - General risk of terrorist attacksElevated - Significant risk of terrorist attacksHigh - High risk of terrorist attacksSevere - Severe risk of terrorist attacksAdministered by the Department of Homeland Security
National Terrorism Advisory SystemElevated Threat - Significant or high risk of terrorist attacksImminent Threat - Critical risk of terrorist attacks