Terror alert systems are standardised emergency population warning systems for describing and disseminating information about terrorism-related threats. They became more popular after the September 11 attacks on the United States in 2001.
National Counter-Terrorism Alert Level
Low - terrorist attack is not expected
Medium - terrorist attack could occur
High - terrorist attack is likely
Extreme - terrorist attack is imminent or has occurred
Administered by the Federal Attorney-General's Department.
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.
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".
Blue - an unconfirmed information about real terroristic threat
Yellow - an confirmed information about real terroristic threat
Red - an information about committed terrorist act
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
Administered by the Joint Terrorist Analysis Centre
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
National Terrorism Advisory System
Elevated Threat - Significant or high risk of terrorist attacks
Imminent Threat - Critical risk of terrorist attacks
